# Quaternion type

Quaternion type
You are encouraged to solve this task according to the task description, using any language you may know.

Quaternions   are an extension of the idea of   complex numbers.

A complex number has a real and complex part,   sometimes written as    a + bi,
where    a    and    b    stand for real numbers, and    i    stands for the square root of minus 1.

An example of a complex number might be    -3 + 2i,
where the real part,    a    is    -3.0    and the complex part,    b    is    +2.0.

A quaternion has one real part and three imaginary parts,    i,     j,    and    k.

A quaternion might be written as    a + bi + cj + dk.

In the quaternion numbering system:

•    i∙i = j∙j = k∙k = i∙j∙k = -1,        or more simply,
•    ii  = jj  = kk  = ijk   = -1.

The order of multiplication is important, as, in general, for two quaternions:

 q1    and    q2:       q1q2 ≠ q2q1.

An example of a quaternion might be    1 +2i +3j +4k

There is a list form of notation where just the numbers are shown and the imaginary multipliers   i,     j,    and    k    are assumed by position.

So the example above would be written as    (1, 2, 3, 4)

Given the three quaternions and their components:

   q  = (1, 2, 3, 4) = (a,  b,  c,  d)
q1 = (2, 3, 4, 5) = (a1, b1, c1, d1)
q2 = (3, 4, 5, 6) = (a2, b2, c2, d2)


And a wholly real number    r = 7.

Create functions   (or classes)   to perform simple maths with quaternions including computing:

1. The norm of a quaternion:
${\displaystyle ={\sqrt {a^{2}+b^{2}+c^{2}+d^{2}}}}$
2. The negative of a quaternion:
 = (-a, -b, -c, -d)
3. The conjugate of a quaternion:
 = ( a, -b, -c, -d)
4. Addition of a real number    r    and a quaternion    q:
 r + q = q + r = (a+r, b, c, d)
 q1 + q2 = (a1+a2, b1+b2, c1+c2, d1+d2)
6. Multiplication of a real number and a quaternion:
 qr = rq = (ar, br, cr, dr)
7. Multiplication of two quaternions    q1    and   q2    is given by:
 ( a1a2 − b1b2 − c1c2 − d1d2,
   a1b2 + b1a2 + c1d2 − d1c2,
   a1c2 − b1d2 + c1a2 + d1b2,
   a1d2 + b1c2 − c1b2 + d1a2 )
8. Show that, for the two quaternions    q1    and    q2: q1q2 ≠ q2q1

If a language has built-in support for quaternions, then use it.

C.f.
•   Vector products
•   On Quaternions;   or on a new System of Imaginaries in Algebra.   By Sir William Rowan Hamilton LL.D, P.R.I.A., F.R.A.S., Hon. M. R. Soc. Ed. and Dub., Hon. or Corr. M. of the Royal or Imperial Academies of St. Petersburgh, Berlin, Turin and Paris, Member of the American Academy of Arts and Sciences, and of other Scientific Societies at Home and Abroad, Andrews' Prof. of Astronomy in the University of Dublin, and Royal Astronomer of Ireland.

## Action!

INCLUDE "H6:REALMATH.ACT"

DEFINE A_="+0"
DEFINE B_="+6"
DEFINE C_="+12"
DEFINE D_="+18"

TYPE Quaternion=[CARD a1,a2,a3,b1,b2,b3,c1,c2,c3,d1,d2,d3]
REAL neg

PROC Init()
ValR("-1",neg)
RETURN

BYTE FUNC Positive(REAL POINTER x)
BYTE ARRAY tmp

tmp=x
IF (tmp(0)&$80)=$00 THEN
RETURN (1)
FI
RETURN (0)

PROC PrintQuat(Quaternion POINTER q)
PrintR(q A_)
IF Positive(q B_) THEN Put('+) FI
PrintR(q B_) Put('i)
IF Positive(q C_) THEN Put('+) FI
PrintR(q C_) Put('j)
IF Positive(q D_) THEN Put('+) FI
PrintR(q D_) Put('k)
RETURN

PROC PrintQuatE(Quaternion POINTER q)
PrintQuat(q) PutE()
RETURN

PROC QuatIntInit(Quaternion POINTER q INT ia,ib,ic,id)
IntToReal(ia,q A_)
IntToReal(ib,q B_)
IntToReal(ic,q C_)
IntToReal(id,q D_)
RETURN

PROC Sqr(REAL POINTER a,b)
RealMult(a,a,b)
RETURN

PROC QuatNorm(Quaternion POINTER q REAL POINTER res)
REAL r1,r2,r3

Sqr(q A_,r1)      ;r1=q.a^2
Sqr(q B_,r2)      ;r2=q.b^2
Sqr(q C_,r1)      ;r1=q.c^2
Sqr(q D_,r1)      ;r1=q.d^2
Sqrt(r3,res)      ;res=sqrt(q.a^2+q.b^2+q.c^2+q.d^2)
RETURN

PROC QuatNegative(Quaternion POINTER q,res)
RealMult(q A_,neg,res A_) ;res.a=-q.a
RealMult(q B_,neg,res B_) ;res.b=-q.b
RealMult(q C_,neg,res C_) ;res.c=-q.c
RealMult(q D_,neg,res D_) ;res.d=-q.d
RETURN

PROC QuatConjugate(Quaternion POINTER q,res)
RealAssign(q A_,res A_)   ;res.a=q.a
RealMult(q B_,neg,res B_) ;res.b=-q.b
RealMult(q C_,neg,res C_) ;res.c=-q.c
RealMult(q D_,neg,res D_) ;res.d=-q.d
RETURN

PROC QuatAddReal(Quaternion POINTER q REAL POINTER r
Quaternion POINTER res)
RealAssign(q B_,res B_) ;res.b=q.b
RealAssign(q C_,res C_) ;res.c=q.c
RealAssign(q D_,res D_) ;res.d=q.d
RETURN

RETURN

PROC QuatMultReal(Quaternion POINTER q REAL POINTER r
Quaternion POINTER res)
RealMult(q A_,r,res A_) ;res.a=q.a*r
RealMult(q B_,r,res B_) ;res.b=q.b*r
RealMult(q C_,r,res C_) ;res.c=q.c*r
RealMult(q D_,r,res D_) ;res.d=q.d*r
RETURN

PROC QuatMult(Quaternion POINTER q1,q2,res)
REAL r1,r2

RealMult(q1 A_,q2 A_,r1) ;r1=q1.a*q2.a
RealMult(q1 B_,q2 B_,r2) ;r2=q1.b*q2.b
RealSub(r1,r2,r3)        ;r3=q1.a*q2.a-q1.b*q2.b
RealMult(q1 C_,q2 C_,r1) ;r1=q1.c*q2.c
RealSub(r3,r1,r2)        ;r2=q1.a*q2.a-q1.b*q2.b-q1.c*q2.c
RealMult(q1 D_,q2 D_,r1) ;r1=q1.d*q2.d
RealSub(r2,r1,res A_)    ;res.a=q1.a*q2.a-q1.b*q2.b-q1.c*q2.c-q1.d*q2.d

RealMult(q1 A_,q2 B_,r1) ;r1=q1.a*q2.b
RealMult(q1 B_,q2 A_,r2) ;r2=q1.b*q2.a
RealMult(q1 C_,q2 D_,r1) ;r1=q1.c*q2.d
RealMult(q1 D_,q2 C_,r1) ;r1=q1.d*q2.c
RealSub(r2,r1,res B_)    ;res.b=q1.a*q2.b+q1.b*q2.a+q1.c*q2.d-q1.d*q2.c

RealMult(q1 A_,q2 C_,r1) ;r1=q1.a*q2.c
RealMult(q1 B_,q2 D_,r2) ;r2=q1.b*q2.d
RealSub(r1,r2,r3)        ;r3=q1.a*q2.c-q1.b*q2.d
RealMult(q1 C_,q2 A_,r1) ;r1=q1.c*q2.a
RealMult(q1 D_,q2 B_,r1) ;r1=q1.d*q2.b

RealMult(q1 A_,q2 D_,r1) ;r1=q1.a*q2.d
RealMult(q1 B_,q2 C_,r2) ;r2=q1.b*q2.c
RealMult(q1 C_,q2 B_,r1) ;r1=q1.c*q2.b
RealSub(r3,r1,r2)        ;r2=q1.a*q2.d+q1.b*q2.c-q1.c*q2.b
RealMult(q1 D_,q2 A_,r1) ;r1=q1.d*q2.a
RETURN

PROC Main()
Quaternion q,q1,q2,q3
REAL r,r2

Put(125) PutE() ;clear the screen
MathInit()
Init()

QuatIntInit(q,1,2,3,4)
QuatIntInit(q1,2,3,4,5)
QuatIntInit(q2,3,4,5,6)
IntToReal(7,r)

Print(" q = ") PrintQuatE(q)
Print("q1 = ") PrintQuatE(q1)
Print("q2 = ") PrintQuatE(q2)
Print(" r = ") PrintRE(r) PutE()

QuatNorm(q,r2) Print(" Norm(q) = ") PrintRE(r2)
QuatNorm(q1,r2) Print("Norm(q1) = ") PrintRE(r2)
QuatNorm(q2,r2) Print("Norm(q2) = ") PrintRE(r2)
QuatNegative(q,q3) Print("      -q = ") PrintQuatE(q3)
QuatConjugate(q,q3) Print(" Conj(q) = ") PrintQuatE(q3)
QuatAddReal(q,r,q3) Print("     q+r = ") PrintQuatE(q3)
QuatAdd(q1,q2,q3) Print("   q1+q2 = ") PrintQuatE(q3)
QuatAdd(q2,q1,q3) Print("   q2+q1 = ") PrintQuatE(q3)
QuatMultReal(q,r,q3) Print("     q*r = ") PrintQuatE(q3)
QuatMult(q1,q2,q3) Print("   q1*q2 = ") PrintQuatE(q3)
QuatMult(q2,q1,q3) Print("   q2*q1 = ") PrintQuatE(q3)
RETURN
Output:
 q = 1+2i+3j+4k
q1 = 2+3i+4j+5k
q2 = 3+4i+5j+6k
r = 7

Norm(q) = 5.47722543
Norm(q1) = 7.34846906
Norm(q2) = 9.27361833
-q = -1-2i-3j-4k
Conj(q) = 1-2i-3j-4k
q+r = 8+2i+3j+4k
q1+q2 = 5+7i+9j+11k
q2+q1 = 5+7i+9j+11k
q*r = 7+14i+21j+28k
q1*q2 = -56+16i+24j+26k
q2*q1 = -56+18i+20j+28k


The package specification (works with any floating-point type):

generic
type Real is digits <>;
package Quaternions is
type Quaternion is record
A, B, C, D : Real;
end record;
function "abs" (Left : Quaternion) return Real;
function Conj (Left : Quaternion) return Quaternion;
function "-" (Left : Quaternion) return Quaternion;
function "+" (Left, Right : Quaternion) return Quaternion;
function "-" (Left, Right : Quaternion) return Quaternion;
function "*" (Left : Quaternion; Right : Real) return Quaternion;
function "*" (Left : Real; Right : Quaternion) return Quaternion;
function "*" (Left, Right : Quaternion) return Quaternion;
function Image (Left : Quaternion) return String;
end Quaternions;


The package implementation:

with Ada.Numerics.Generic_Elementary_Functions;
package body Quaternions is
package Elementary_Functions is
use Elementary_Functions;
function "abs" (Left : Quaternion) return Real is
begin
return Sqrt (Left.A**2 + Left.B**2 + Left.C**2 + Left.D**2);
end "abs";
function Conj (Left : Quaternion) return Quaternion is
begin
return (A => Left.A, B => -Left.B, C => -Left.C, D => -Left.D);
end Conj;
function "-" (Left : Quaternion) return Quaternion is
begin
return (A => -Left.A, B => -Left.B, C => -Left.C, D => -Left.D);
end "-";
function "+" (Left, Right : Quaternion) return Quaternion is
begin
return
(  A => Left.A + Right.A, B => Left.B + Right.B,
C => Left.C + Right.C, D => Left.D + Right.D
);
end "+";
function "-" (Left, Right : Quaternion) return Quaternion is
begin
return
(  A => Left.A - Right.A, B => Left.B - Right.B,
C => Left.C - Right.C, D => Left.D - Right.D
);
end "-";
function "*" (Left : Quaternion; Right : Real) return Quaternion is
begin
return
(  A => Left.A * Right, B => Left.B * Right,
C => Left.C * Right, D => Left.D * Right
);
end "*";
function "*" (Left : Real; Right : Quaternion) return Quaternion is
begin
return Right * Left;
end "*";
function "*" (Left, Right : Quaternion) return Quaternion is
begin
return
(  A => Left.A * Right.A - Left.B * Right.B - Left.C * Right.C - Left.D * Right.D,
B => Left.A * Right.B + Left.B * Right.A + Left.C * Right.D - Left.D * Right.C,
C => Left.A * Right.C - Left.B * Right.D + Left.C * Right.A + Left.D * Right.B,
D => Left.A * Right.D + Left.B * Right.C - Left.C * Right.B + Left.D * Right.A
);
end "*";
function Image (Left : Quaternion) return String is
begin
return Real'Image (Left.A) & " +"  &
Real'Image (Left.B) & "i +" &
Real'Image (Left.C) & "j +" &
Real'Image (Left.D) & "k";
end Image;
end Quaternions;


Test program:

with Ada.Text_IO;  use Ada.Text_IO;
with Quaternions;
procedure Test_Quaternion is
package Float_Quaternion is new Quaternions (Float);
use Float_Quaternion;
q  : Quaternion := (1.0, 2.0, 3.0, 4.0);
q1 : Quaternion := (2.0, 3.0, 4.0, 5.0);
q2 : Quaternion := (3.0, 4.0, 5.0, 6.0);
r  : Float      := 7.0;
begin
Put_Line ("q = "       & Image (q));
Put_Line ("q1 = "      & Image (q1));
Put_Line ("q2 = "      & Image (q2));
Put_Line ("r ="        & Float'Image (r));
Put_Line ("abs q ="    & Float'Image (abs q));
Put_Line ("abs q1 ="   & Float' Image (abs q1));
Put_Line ("abs q2 ="   & Float' Image (abs q2));
Put_Line ("-q = "      & Image (-q));
Put_Line ("conj q = "  & Image (Conj (q)));
Put_Line ("q1 + q2 = " & Image (q1 + q2));
Put_Line ("q2 + q1 = " & Image (q2 + q1));
Put_Line ("q * r = "   & Image (q * r));
Put_Line ("r * q = "   & Image (r * q));
Put_Line ("q1 * q2 = " & Image (q1 * q2));
Put_Line ("q2 * q1 = " & Image (q2 * q1));
end Test_Quaternion;

Output:
q =  1.00000E+00 + 2.00000E+00i + 3.00000E+00j + 4.00000E+00k
q1 =  2.00000E+00 + 3.00000E+00i + 4.00000E+00j + 5.00000E+00k
q2 =  3.00000E+00 + 4.00000E+00i + 5.00000E+00j + 6.00000E+00k
r = 7.00000E+00
abs q = 5.47723E+00
abs q1 = 7.34847E+00
abs q2 = 9.27362E+00
-q = -1.00000E+00 +-2.00000E+00i +-3.00000E+00j +-4.00000E+00k
conj q =  1.00000E+00 +-2.00000E+00i +-3.00000E+00j +-4.00000E+00k
q1 + q2 =  5.00000E+00 + 7.00000E+00i + 9.00000E+00j + 1.10000E+01k
q2 + q1 =  5.00000E+00 + 7.00000E+00i + 9.00000E+00j + 1.10000E+01k
q * r =  7.00000E+00 + 1.40000E+01i + 2.10000E+01j + 2.80000E+01k
r * q =  7.00000E+00 + 1.40000E+01i + 2.10000E+01j + 2.80000E+01k
q1 * q2 = -5.60000E+01 + 1.60000E+01i + 2.40000E+01j + 2.60000E+01k
q2 * q1 = -5.60000E+01 + 1.80000E+01i + 2.00000E+01j + 2.80000E+01k


## ALGOL 68

Translation of: python

Note: This specimen retains the original python coding style.

Works with: ALGOL 68 version Revision 1 - one minor extension to language used - PRAGMA READ, similar to C's #include directive.
Works with: ALGOL 68G version Any - tested with release algol68g-2.6.

File: prelude/Quaternion.a68

# -*- coding: utf-8 -*- #

COMMENT REQUIRES:
MODE QUATSCAL = REAL; # Scalar #
QUATSCAL quat small scal = small real;
END COMMENT

# PROVIDES: #
FORMAT quat scal fmt := $g(-0, 4)$;
FORMAT signed fmt = $b("+", "")f(quat scal fmt)$;

FORMAT quat fmt = $f(quat scal fmt)"+"f(quat scal fmt)"i+"f(quat scal fmt)"j+"f(quat scal fmt)"k"$;
FORMAT squat fmt = $f(signed fmt)f(signed fmt)"i"f(signed fmt)"j"f(signed fmt)"k"$;

MODE QUAT = STRUCT(QUATSCAL r, i, j, k);
QUAT i=(0, 1, 0, 0),
j=(0, 0, 1, 0),
k=(0, 0, 0, 1);

MODE QUATCOSCAL = UNION(INT, SHORT REAL, SHORT INT);
MODE QUATSUBSCAL = UNION(QUATCOSCAL, QUATSCAL);

MODE COMPLSCAL = STRUCT(QUATSCAL r, im);
# compatable but not the same #
MODE ISOQUAT = UNION([]REAL, []INT, []SHORT REAL, []SHORT INT, []QUATSCAL);
MODE COQUAT  = UNION(COMPLSCAL, QUATCOSCAL, ISOQUAT);
MODE SUBQUAT = UNION(COQUAT, QUAT); # subset is itself #

MODE QUATERNION = QUAT;

PROC quat fix type error = (QUAT quat, []STRING msg)BOOL: (
putf(stand error, ($"Type error:"$,$" "g$, msg, quat fmt, quat, $l$));
stop
);

COMMENT
For a list of coercions expected in A68 c.f.
* http://rosettacode.org/wiki/ALGOL_68#Coercion_.28casting.29 # ...

Pre-Strong context: Deproceduring, dereferencing & uniting. e.g. OP arguments
* soft(deproceduring for assignment),
* weak(dereferencing for slicing and OF selection),
* meek(dereferencing for indexing, enquiries and PROC calls),
* firm(uniting of OPerators),
Strong context only: widening (INT=>REAL=>COMPL), rowing (REAL=>[]REAL) & voiding
* strong(widening,rowing,voiding for identities/initialisations, arguments and casts et al)
Key points:
* arguments to OPerators do not widen or row!
* UNITING is permitted in OP/String ccontext.

There are 4 principle scenerios for most operators:
+---------------+-------------------------------+-------------------------------+
|  OP e.g. *    |  SCALar                       |  QUATernion                   |
+---------------+-------------------------------+-------------------------------+
|  SCALar       |  SCAL * SCAL ... inherit      |  SCAL * QUAT                  |
+---------------+-------------------------------+-------------------------------+
|  QUATernion   |  QUAT * SCAL                  |  QUAT * QUAT                  |
+---------------+-------------------------------+-------------------------------+
However this is compounded with SUBtypes of the SCALar & isomorphs the QUATernion,
e.g.
* SCAL may be a superset of SHORT REAL or INT - a widening coercion is required
* QUAT may be a superset eg of COMPL or [4]INT
* QUAT may be a structural isomorph eg of [4]REAL
+---------------+---------------+---------------+---------------+---------------+
|  OP e.g. *    |  SUBSCAL      |  SCALar       |  COQUAT       |  QUATernion   |
+---------------+---------------+---------------+---------------+---------------+
|  SUBSCAL      |                               |  inherit      |  SUBSCAT*QUAT |
+---------------+           inherit             +---------------+---------------+
|  SCALar       |                               |  inherit      |  SCAL * QUAT  |
+---------------+---------------+---------------+---------------+---------------+
|  COQUAT       |  inherit      |  inherit      |  inherit      |  COQUAT*QUAT  |
+---------------+---------------+---------------+---------------+---------------+
|  QUATernion   | QUAT*SUBSCAL  |  QUAT*SCAL    | QUAT * COQUAT |  QUAT * QUAT  |
+---------------+---------------+---------------+---------------+---------------+
Keypoint: if an EXPLICIT QUAT is not involved, then we can simple inherit, OR QUATINIT!
END COMMENT

MODE CLASSQUAT = STRUCT(
PROC (REF QUAT #new#, QUATSCAL #r#, QUATSCAL #i#, QUATSCAL #j#, QUATSCAL #k#)REF QUAT new,
PROC (REF QUAT #self#)QUAT conjugate,
PROC (REF QUAT #self#)QUATSCAL norm sq,
PROC (REF QUAT #self#)QUATSCAL norm,
PROC (REF QUAT #self#)QUAT reciprocal,
PROC (REF QUAT #self#)STRING repr,
PROC (REF QUAT #self#)QUAT neg,
PROC (REF QUAT #self#, SUBQUAT #other#)QUAT add,
PROC (REF QUAT #self#, SUBQUAT #other#)QUAT radd,
PROC (REF QUAT #self#, SUBQUAT #other#)QUAT sub,
PROC (REF QUAT #self#, SUBQUAT #other#)QUAT mul,
PROC (REF QUAT #self#, SUBQUAT #other#)QUAT rmul,
PROC (REF QUAT #self#, SUBQUAT #other#)QUAT div,
PROC (REF QUAT #self#, SUBQUAT #other#)QUAT rdiv,
PROC (REF QUAT #self#)QUAT exp
);

CLASSQUAT class quat = (

# PROC new =#(REF QUAT new, QUATSCAL r, i, j, k)REF QUAT: (
# 'Defaults all parts of quaternion to zero' #
IF new ISNT REF QUAT(NIL) THEN new ELSE HEAP QUAT FI := (r, i, j, k)
),

# PROC conjugate =#(REF QUAT self)QUAT:
(r OF self, -i OF self, -j OF self, -k OF self),

# PROC norm sq =#(REF QUAT self)QUATSCAL:
r OF self**2 + i OF self**2 + j OF self**2 + k OF self**2,

# PROC norm =#(REF QUAT self)QUATSCAL:
sqrt((norm sq OF class quat)(self)),

# PROC reciprocal =#(REF QUAT self)QUAT:(
QUATSCAL n2 = (norm sq OF class quat)(self);
QUAT conj = (conjugate OF class quat)(self);
(r OF conj/n2, i OF conj/n2, j OF conj/n2, k OF conj/n2)
),

# PROC repr =#(REF QUAT self)STRING: (
# 'Shorter form of Quaternion as string' #
FILE f; STRING s; associate(f, s);
putf(f, (squat fmt, r OF self>=0, r OF self,
i OF self>=0, i OF self, j OF self>=0, j OF self, k OF self>=0, k OF self));
close(f);
s
),

# PROC neg =#(REF QUAT self)QUAT:
(-r OF self, -i OF self, -j OF self, -k OF self),

# PROC add =#(REF QUAT self, SUBQUAT other)QUAT:
CASE other IN
(QUAT other): (r OF self + r OF other, i OF self + i OF other, j OF self + j OF other, k OF self + k OF other),
(QUATSUBSCAL other): (r OF self + QUATSCALINIT other, i OF self, j OF self, k OF self)
OUT IF quat fix type error(SKIP,"in add") THEN SKIP ELSE stop FI
ESAC,

# PROC radd =#(REF QUAT self, SUBQUAT other)QUAT:

# PROC sub =#(REF QUAT self, SUBQUAT other)QUAT:
CASE other IN
(QUAT other): (r OF self - r OF other, i OF self - i OF other, j OF self - j OF other, k OF self - k OF other),
(QUATSCAL other): (r OF self - other, i OF self, j OF self, k OF self)
OUT IF quat fix type error(self,"in sub") THEN SKIP ELSE stop FI
ESAC,

# PROC mul =#(REF QUAT self, SUBQUAT other)QUAT:
CASE other IN
(QUAT other):(
r OF self*r OF other - i OF self*i  OF other - j OF self*j  OF other - k OF self*k  OF other,
r OF self*i  OF other + i OF self*r OF other + j OF self*k  OF other - k OF self*j  OF other,
r OF self*j  OF other - i OF self*k  OF other + j OF self*r OF other + k OF self*i  OF other,
r OF self*k  OF other + i OF self*j  OF other - j OF self*i  OF other + k OF self*r OF other
),
(QUATSCAL other): ( r OF self * other, i OF self * other, j OF self * other, k OF self * other)
OUT IF quat fix type error(self,"in mul") THEN SKIP ELSE stop FI
ESAC,

# PROC rmul =#(REF QUAT self, SUBQUAT other)QUAT:
CASE other IN
(QUAT other): (mul OF class quat)(LOC QUAT := other, self),
(QUATSCAL other): (mul OF class quat)(self, other)
OUT IF quat fix type error(self,"in rmul") THEN SKIP ELSE stop FI
ESAC,

# PROC div =#(REF QUAT self, SUBQUAT other)QUAT:
CASE other IN
(QUAT other): (mul OF class quat)(self, (reciprocal OF class quat)(LOC QUAT := other)),
(QUATSCAL other): (mul OF class quat)(self, 1/other)
OUT IF quat fix type error(self,"in div") THEN SKIP ELSE stop FI
ESAC,

# PROC rdiv =#(REF QUAT self, SUBQUAT other)QUAT:
CASE other IN
(QUAT other): (div OF class quat)(LOC QUAT := other, self),
(QUATSCAL other): (div OF class quat)(LOC QUAT := (other, 0, 0, 0), self)
OUT IF quat fix type error(self,"in rdiv") THEN SKIP ELSE stop FI
ESAC,

# PROC exp =#(REF QUAT self)QUAT: (
QUAT fac := self;
QUAT sum := 1.0 + fac;
FOR i FROM 2 TO bits width WHILE ABS(fac + quat small scal) /= quat small scal DO
VOID(sum +:= (fac *:= self / ##QUATSCAL(i)))
OD;
sum
)
);

PRIO INIT = 1;
OP QUATSCALINIT = (QUATSUBSCAL scal)QUATSCAL:
CASE scal IN
(INT scal): scal,
(SHORT INT scal): scal,
(SHORT REAL scal): scal
OUT IF quat fix type error(SKIP,"in QUATSCALINIT") THEN SKIP ELSE stop FI
ESAC;

OP INIT = (REF QUAT new, SUBQUAT from)REF QUAT:
new :=
CASE from IN
(QUATSUBSCAL scal):(QUATSCALINIT scal, 0, 0, 0)
#(COQUAT rijk):(new OF class quat)(LOC QUAT := new, rijk[1], rijk[2], rijk[3], rijk[4]),#
OUT IF quat fix type error(SKIP,"in INIT") THEN SKIP ELSE stop FI
ESAC;

OP QUATINIT = (COQUAT lhs)REF QUAT: (HEAP QUAT)INIT lhs;

OP +    = (QUAT q)QUAT:   q,
-    = (QUAT q)QUAT:   (neg  OF class quat)(LOC QUAT := q),
CONJ = (QUAT q)QUAT:   (conjugate OF class quat)(LOC QUAT := q),
ABS  = (QUAT q)QUATSCAL:   (norm OF class quat)(LOC QUAT := q),
REPR = (QUAT q)STRING: (repr OF class quat)(LOC QUAT := q);
# missing: Diadic: I, J, K END #

OP +:= = (REF QUAT a, QUAT b)QUAT: a:=( add OF class quat)(a, b),
+:= = (REF QUAT a, COQUAT b)QUAT: a:=( add OF class quat)(a, b),
+=: = (QUAT a, REF QUAT b)QUAT: b:=(radd OF class quat)(b, a),
+=: = (COQUAT a, REF QUAT b)QUAT: b:=(radd OF class quat)(b, a);
# missing: Worthy PLUSAB, PLUSTO for SHORT/LONG INT QUATSCAL & COMPL #

OP -:= = (REF QUAT a, QUAT b)QUAT: a:=( sub OF class quat)(a, b),
-:= = (REF QUAT a, COQUAT b)QUAT: a:=( sub OF class quat)(a, b);
# missing: Worthy MINUSAB for SHORT/LONG INT ##COQUAT & COMPL #

PRIO *=: = 1, /=: = 1;
OP *:= = (REF QUAT a, QUAT b)QUAT: a:=( mul OF class quat)(a, b),
*:= = (REF QUAT a, COQUAT b)QUAT: a:=( mul OF class quat)(a, b),
*=: = (QUAT a, REF QUAT b)QUAT: b:=(rmul OF class quat)(b, a),
*=: = (COQUAT a, REF QUAT b)QUAT: b:=(rmul OF class quat)(b, a);
# missing: Worthy TIMESAB, TIMESTO for SHORT/LONG INT ##COQUAT & COMPL #

OP /:= = (REF QUAT a, QUAT b)QUAT: a:=( div OF class quat)(a, b),
/:= = (REF QUAT a, COQUAT b)QUAT: a:=( div OF class quat)(a, b),
/=: = (QUAT a, REF QUAT b)QUAT: b:=(rdiv OF class quat)(b, a),
/=: = (COQUAT a, REF QUAT b)QUAT: b:=(rdiv OF class quat)(b, a);
# missing: Worthy OVERAB, OVERTO for SHORT/LONG INT ##COQUAT & COMPL #

OP + = (QUAT a, b)QUAT:      ( add OF class quat)(LOC QUAT := a, b),
+ = (QUAT a, COQUAT b)QUAT: ( add OF class quat)(LOC QUAT := a, b),
+ = (COQUAT a, QUAT b)QUAT: (radd OF class quat)(LOC QUAT := b, a);

OP - = (QUAT a, b)QUAT:      ( sub OF class quat)(LOC QUAT := a, b),
- = (QUAT a, COQUAT b)QUAT: ( sub OF class quat)(LOC QUAT := a, b),
- = (COQUAT a, QUAT b)QUAT:-( sub OF class quat)(LOC QUAT := b, a);

OP * = (QUAT a, b)QUAT:      ( mul OF class quat)(LOC QUAT := a, b),
* = (QUAT a, COQUAT b)QUAT: ( mul OF class quat)(LOC QUAT := a, b),
* = (COQUAT a, QUAT b)QUAT: (rmul OF class quat)(LOC QUAT := b, a);

OP / = (QUAT a, b)QUAT:      ( div OF class quat)(LOC QUAT := a, b),
/ = (QUAT a, COQUAT b)QUAT: ( div OF class quat)(LOC QUAT := a, b),
/ = (COQUAT a, QUAT b)QUAT:
( div OF class quat)(LOC QUAT := QUATINIT 1, a);

PROC quat exp = (QUAT q)QUAT:   (exp OF class quat)(LOC QUAT := q);

SKIP # missing: quat arc{sin, cos, tan}h, log, exp, ln etc END #

File: test/Quaternion.a68

#!/usr/bin/a68g --script #
# -*- coding: utf-8 -*- #

# REQUIRES: #
MODE QUATSCAL = REAL; # Scalar #
QUATSCAL quat small scal = small real;

test:(
REAL r = 7;
QUAT q  = (1, 2, 3, 4),
q1 = (2, 3, 4, 5),
q2 = (3, 4, 5, 6);

printf((
$"r = " f(quat scal fmt)l$, r,
$"q = " f(quat fmt)l$, q,
$"q1 = " f(quat fmt)l$, q1,
$"q2 = " f(quat fmt)l$, q2,
$"ABS q = " f(quat scal fmt)", "$, ABS q,
$"ABS q1 = " f(quat scal fmt)", "$, ABS q1,
$"ABS q2 = " f(quat scal fmt)l$, ABS q2,
$"-q = " f(quat fmt)l$, -q,
$"CONJ q = " f(quat fmt)l$, CONJ q,
$"r + q = " f(quat fmt)l$, r + q,
$"q + r = " f(quat fmt)l$, q + r,
$"q1 + q2 = "f(quat fmt)l$, q1 + q2,
$"q2 + q1 = "f(quat fmt)l$, q2 + q1,
$"q * r = " f(quat fmt)l$, q * r,
$"r * q = " f(quat fmt)l$, r * q,
$"q1 * q2 = "f(quat fmt)l$, q1 * q2,
$"q2 * q1 = "f(quat fmt)l$, q2 * q1
));

CO
$"ASSERT q1 * q2 != q2 * q1 = "f(quat fmt)l$, ASSERT q1 * q2 != q2 * q1, $l$;
END CO

printf((
$"i*i = " f(quat fmt)l$, i*i,
$"j*j = " f(quat fmt)l$, j*j,
$"k*k = " f(quat fmt)l$, k*k,
$"i*j*k = " f(quat fmt)l$, i*j*k,
$"q1 / q2 = " f(quat fmt)l$, q1 / q2,
$"q1 / q2 * q2 = "f(quat fmt)l$, q1 / q2 * q2,
$"q2 * q1 / q2 = "f(quat fmt)l$, q2 * q1 / q2,
$"1/q1 * q1 = " f(quat fmt)l$, 1.0/q1 * q1,
$"q1 / q1 = " f(quat fmt)l$, q1 / q1,
$"quat exp(pi * i) = " f(quat fmt)l$, quat exp(pi * i),
$"quat exp(pi * j) = " f(quat fmt)l$, quat exp(pi * j),
$"quat exp(pi * k) = " f(quat fmt)l$, quat exp(pi * k)
));
print((REPR(-q1*q2), ", ", REPR(-q2*q1), new line))
)
Output:
r = 7.0000
q = 1.0000+2.0000i+3.0000j+4.0000k
q1 = 2.0000+3.0000i+4.0000j+5.0000k
q2 = 3.0000+4.0000i+5.0000j+6.0000k
ABS q = 5.4772, ABS q1 = 7.3485, ABS q2 = 9.2736
-q = -1.0000+-2.0000i+-3.0000j+-4.0000k
CONJ q = 1.0000+-2.0000i+-3.0000j+-4.0000k
r + q = 8.0000+2.0000i+3.0000j+4.0000k
q + r = 8.0000+2.0000i+3.0000j+4.0000k
q1 + q2 = 5.0000+7.0000i+9.0000j+11.0000k
q2 + q1 = 5.0000+7.0000i+9.0000j+11.0000k
q * r = 7.0000+14.0000i+21.0000j+28.0000k
r * q = 7.0000+14.0000i+21.0000j+28.0000k
q1 * q2 = -56.0000+16.0000i+24.0000j+26.0000k
q2 * q1 = -56.0000+18.0000i+20.0000j+28.0000k
i*i = -1.0000+.0000i+.0000j+.0000k
j*j = -1.0000+.0000i+.0000j+.0000k
k*k = -1.0000+.0000i+.0000j+.0000k
i*j*k = -1.0000+.0000i+.0000j+.0000k
q1 / q2 = .7907+.0233i+-.0000j+.0465k
q1 / q2 * q2 = 2.0000+3.0000i+4.0000j+5.0000k
q2 * q1 / q2 = 2.0000+3.4651i+3.9070j+4.7674k
1/q1 * q1 = 2.0000+3.0000i+4.0000j+5.0000k
q1 / q1 = 1.0000+.0000i+.0000j+.0000k
quat exp(pi * i) = -1.0000+.0000i+.0000j+.0000k
quat exp(pi * j) = -1.0000+.0000i+.0000j+.0000k
quat exp(pi * k) = -1.0000+.0000i+.0000j+.0000k
+56.0000-16.0000i-24.0000j-26.0000k, +56.0000-18.0000i-20.0000j-28.0000k


## ALGOL W

begin
% Quaternion record type                                                 %
record Quaternion ( real a, b, c, d );

% returns the norm of the specified quaternion                           %
real procedure normQ ( reference(Quaternion) value q ) ;
sqrt( (a(q) * a(q)) + (b(q) * b(q)) + (c(q) * c(q)) + (d(q) * d(q)) );

% returns the negative of the specified quaternion                       %
reference(Quaternion) procedure negQ ( reference(Quaternion) value q ) ;
Quaternion( - a(q), - b(q), - c(q), - d(q) );

% returns the conjugate of the specified quaternion                      %
reference(Quaternion) procedure conjQ ( reference(Quaternion) value q ) ;
Quaternion(   a(q), - b(q), - c(q), - d(q) );

% returns the sum of a real and a quaternion                             %
reference(Quaternion) procedure addRQ ( real                  value r
; reference(Quaternion) value q
) ;
Quaternion( r + a(q), b(q), c(q), d(q) );

% returns the sum of a quaternion and a real                             %
reference(Quaternion) procedure addQR ( reference(Quaternion) value q
; real                  value r
) ;
Quaternion( r + a(q), b(q), c(q), d(q) );

% returns the sum of the specified quaternions                           %
reference(Quaternion) procedure addQQ ( reference(Quaternion) value q1
; reference(Quaternion) value q2
) ;
Quaternion( a(q1) + a(q2), b(q1) + b(q2), c(q1) + c(q2), d(q1) + d(q2) );

% returns the specified quaternion multiplied by a real                  %
reference(Quaternion) procedure mulQR ( reference(Quaternion) value q
; real                  value r
) ;
Quaternion( r * a(q), r * b(q), r * c(q), r * d(q) );

% returns a real multiplied by the specified quaternion                  %
reference(Quaternion) procedure mulRQ ( real                  value r
; reference(Quaternion) value q
) ;
mulQR( q, r );

% returns the Quaternion product of the specified quaternions            %
reference(Quaternion) procedure mulQQ( reference(Quaternion) value q1
; reference(Quaternion) value q2
) ;
Quaternion( (a(q1) * a(q2)) - (b(q1) * b(q2)) - (c(q1) * c(q2)) - (d(q1) * d(q2))
, (a(q1) * b(q2)) + (b(q1) * a(q2)) + (c(q1) * d(q2)) - (d(q1) * c(q2))
, (a(q1) * c(q2)) - (b(q1) * d(q2)) + (c(q1) * a(q2)) + (d(q1) * b(q2))
, (a(q1) * d(q2)) + (b(q1) * c(q2)) - (c(q1) * b(q2)) + (d(q1) * a(q2))
);

% returns true if the two quaternions are equal, false otherwise         %
logical procedure equalQ( reference(Quaternion) value q1
; reference(Quaternion) value q2
) ;
a(q1) = a(q2) and b(q1) = b(q2) and c(q1) = c(q2) and d(q1) = d(q2);

% writes a quaternion                                                    %
procedure writeonQ( reference(Quaternion) value q ) ;
writeon( "(", a(q), ", ", b(q), ", ", c(q), ", ", d(q), ")" );

% test q1q2 = q2q1                                                       %
reference(Quaternion) q, q1, q2;

q  := Quaternion( 1, 2, 3, 4 );
q1 := Quaternion( 2, 3, 4, 5 );
q2 := Quaternion( 3, 4, 5, 6 );

% set output format                                                      %
s_w := 0; r_format := "A"; r_w := 5; r_d := 1;

write( "      q:" );writeonQ( q );
write( "     q1:" );writeonQ( q1 );
write( "     q2:" );writeonQ( q2 );
write( "norm  q:" );writeon( normQ( q ) );
write( "norm q1:" );writeon( normQ( q1 ) );
write( "norm q2:" );writeon( normQ( q2 ) );

write( " conj q:" );writeonQ( conjQ( q ) );
write( "    - q:" );writeonQ( negQ( q ) );
write( "  7 + q:" );writeonQ( addRQ( 7, q ) );
write( "  q + 9:" );writeonQ( addQR( q, 9 ) );
write( " q + q1:" );writeonQ( addQQ( q, q1 ) );
write( "  3 * q:" );writeonQ( mulRQ( 3, q ) );
write( "  q * 4:" );writeonQ( mulQR( q, 4 ) );

% check that q1q2 not = q2q1                                             %
if equalQ( mulQQ( q1, q2 ), mulQQ( q2, q1 ) )
then write( "q1q2 = q2q1 ??" )
else write( "q1q2 <> q2q1" );

write( "   q1q2:" );writeonQ( mulQQ( q1, q2 ) );
write( "   q2q1:" );writeonQ( mulQQ( q2, q1 ) );

end.
Output:
      q:(  1.0,   2.0,   3.0,   4.0)
q1:(  2.0,   3.0,   4.0,   5.0)
q2:(  3.0,   4.0,   5.0,   6.0)
norm  q:  5.4
norm q1:  7.3
norm q2:  9.2
conj q:(  1.0,  -2.0,  -3.0,  -4.0)
- q:( -1.0,  -2.0,  -3.0,  -4.0)
7 + q:(  8.0,   2.0,   3.0,   4.0)
q + 9:( 10.0,   2.0,   3.0,   4.0)
q + q1:(  3.0,   5.0,   7.0,   9.0)
3 * q:(  3.0,   6.0,   9.0,  12.0)
q * 4:(  4.0,   8.0,  12.0,  16.0)
q1q2 <> q2q1
q1q2:(-56.0,  16.0,  24.0,  26.0)
q2q1:(-56.0,  18.0,  20.0,  28.0)


## Arturo

qnorm: $=> [sqrt fold & [x y] -> x + y*y] qneg:$ => [map & => neg]

qconj: $[q] [@[q\0] ++ qneg drop q] qaddr: function [q r][ [a b c d]: q @[a+r b c d] ] qadd:$ => [map couple & & => sum]

qmulr: $[q r] [map q'x -> x*r] qmul: function [q1 q2][ [a1 b1 c1 d1]: q1 [a2 b2 c2 d2]: q2 @[ (((a1*a2) - b1*b2) - c1*c2) - d1*d2, (((a1*b2) + b1*a2) + c1*d2) - d1*c2, (((a1*c2) - b1*d2) + c1*a2) + d1*b2, (((a1*d2) + b1*c2) - c1*b2) + d1*a2 ] ] ; --- test quaternions --- q: [1 2 3 4] q1: [2 3 4 5] q2: [3 4 5 6] r: 7 print ['qnorm q '= qnorm q] print ['qneg q '= qneg q] print ['qconj q '= qconj q] print ['qaddr q r '= qaddr q r] print ['qmulr q r '= qmulr q r] print ['qadd q1 q2 '= qadd q1 q2] print ['qmul q1 q2 '= qmul q1 q2] print ['qmul q2 q1 '= qmul q2 q1]  Output: qnorm [1 2 3 4] = 5.477225575051661 qneg [1 2 3 4] = [-1 -2 -3 -4] qconj [1 2 3 4] = [1 -2 -3 -4] qaddr [1 2 3 4] 7 = [8 2 3 4] qmulr [1 2 3 4] 7 = [7 14 21 28] qadd [2 3 4 5] [3 4 5 6] = [5 7 9 11] qmul [2 3 4 5] [3 4 5 6] = [-56 16 24 26] qmul [3 4 5 6] [2 3 4 5] = [-56 18 20 28] ## ATS Library: ats2-xprelude //-------------------------------------------------------------------- #include "share/atspre_staload.hats" //-------------------------------------------------------------------- (* Here is one way to get a sqrt function without going beyond the ATS prelude. The prelude (at the time of this writing) contains some templates for which implementations were never added. Here I add an implementation. The ats2-xprelude package at https://sourceforge.net/p/chemoelectric/ats2-xprelude contains a much more extensive and natural interface to the C math library. *) %{^ #include <math.h> %} implement (* "Generic" square root. *) gsqrt_val<double> x = (* Call "sqrt" from the C math library. *)$extfcall (double, "sqrt", x)

//--------------------------------------------------------------------

abst@ype quaternion (tk : tkind) =
(* The following determines the SIZE of a quaternion, but not its
actual representation: *)
@(g0float tk, g0float tk, g0float tk, g0float tk)

extern fn {tk : tkind} quaternion_make :
(g0float tk, g0float tk, g0float tk, g0float tk) -<> quaternion tk

extern fn {tk : tkind} fprint_quaternion :
(FILEref, quaternion tk) -> void
extern fn {tk : tkind} print_quaternion :
quaternion tk -> void

extern fn {tk : tkind} quaternion_norm_squared :
quaternion tk -<> g0float tk
extern fn {tk : tkind} quaternion_norm :
quaternion tk -< !exn > g0float tk

extern fn {tk : tkind} quaternion_neg :
quaternion tk -<> quaternion tk
extern fn {tk : tkind} quaternion_conj :
quaternion tk -<> quaternion tk

extern fn {tk : tkind} add_quaternion_g0float :
(quaternion tk, g0float tk) -<> quaternion tk
extern fn {tk : tkind} add_g0float_quaternion :
(g0float tk, quaternion tk) -<> quaternion tk
extern fn {tk : tkind} add_quaternion_quaternion :
(quaternion tk, quaternion tk) -<> quaternion tk

extern fn {tk : tkind} mul_quaternion_g0float :
(quaternion tk, g0float tk) -<> quaternion tk
extern fn {tk : tkind} mul_g0float_quaternion :
(g0float tk, quaternion tk) -<> quaternion tk
extern fn {tk : tkind} mul_quaternion_quaternion :
(quaternion tk, quaternion tk) -<> quaternion tk

extern fn {tk : tkind} quaternion_eq :
(quaternion tk, quaternion tk) -<> bool

//--------------------------------------------------------------------

local

(* Now we decide the REPRESENTATION of a quaternion. A quaternion is
represented as an unboxed 4-tuple of "real" numbers of any one
particular typekind. *)
typedef _quaternion (tk : tkind) =
@(g0float tk, g0float tk, g0float tk, g0float tk)

assume quaternion tk = _quaternion tk

in (* local *)

implement {tk}
quaternion_make (a, b, c, d) =
@(a, b, c, d)

implement {tk}
fprint_quaternion (outf, q) =
let
typedef t = g0float tk
val @(a, b, c, d) = q
in
fprint_val<t> (outf, a);
if g0i2f 0 <= b then fprint_val<string> (outf, "+");
fprint_val<t> (outf, b);
fprint_val<string> (outf, "i");
if g0i2f 0 <= c then fprint_val<string> (outf, "+");
fprint_val<t> (outf, c);
fprint_val<string> (outf, "j");
if g0i2f 0 <= d then fprint_val<string> (outf, "+");
fprint_val<t> (outf, d);
fprint_val<string> (outf, "k");
end

implement {tk}
print_quaternion q =
fprint_quaternion (stdout_ref, q)

implement {tk}
quaternion_norm_squared q =
let
val @(a, b, c, d) = q
in
(a * a) + (b * b) + (c * c) + (d * d)
end

implement {tk}
quaternion_norm q =
gsqrt_val<g0float tk> (quaternion_norm_squared q)

implement {tk}
quaternion_neg q =
let
val @(a, b, c, d) = q
in
@(~a, ~b, ~c, ~d)
end

implement {tk}
quaternion_conj q =
let
val @(a, b, c, d) = q
in
@(a, ~b, ~c, ~d)
end

implement {tk}
let
val @(a, b, c, d) = q
in
@(a + r, b, c, d)
end

implement {tk}
let
val @(a, b, c, d) = q
in
@(r + a, b, c, d)
end

implement {tk}
let
val @(a1, b1, c1, d1) = q1
and @(a2, b2, c2, d2) = q2
in
@(a1 + a2, b1 + b2, c1 + c2, d1 + d2)
end

implement {tk}
mul_quaternion_g0float (q, r) =
let
val @(a, b, c, d) = q
in
@(a * r, b * r, c * r, d * r)
end

implement {tk}
mul_g0float_quaternion (r, q) =
let
val @(a, b, c, d) = q
in
@(r * a, r * b, r * c, r * d)
end

implement {tk}
mul_quaternion_quaternion (q1, q2) =
let
val @(a1, b1, c1, d1) = q1
and @(a2, b2, c2, d2) = q2
in
@((a1 * a2) - (b1 * b2) - (c1 * c2) - (d1 * d2),
(a1 * b2) + (b1 * a2) + (c1 * d2) - (d1 * c2),
(a1 * c2) - (b1 * d2) + (c1 * a2) + (d1 * b2),
(a1 * d2) + (b1 * c2) - (c1 * b2) + (d1 * a2))
end

implement {tk}
quaternion_eq (q1, q2) =
let
val @(a1, b1, c1, d1) = q1
and @(a2, b2, c2, d2) = q2
in
(a1 = a2) * (b1 = b2) * (c1 = c2) * (d1 = d2)
end

end (* local *)

//--------------------------------------------------------------------

val q = quaternion_make (1.0, 2.0, 3.0, 4.0)
and q1 = quaternion_make (2.0, 3.0, 4.0, 5.0)
and q2 = quaternion_make (3.0, 4.0, 5.0, 6.0)
and r = 7.0

implement
main0 () =
let
(* Let us print double precision numbers in a format more readable
than is the prelude's default. *)
implement
fprint_val<double> (outf, x) =
let
typedef f = $extype"FILE *" val _ =$extfcall (int, "fprintf", $UNSAFE.cast{f} outf, "%g", x) in end in println! ("q = ", q); println! ("q1 = ", q1); println! ("q2 = ", q2); println! (); println! ("||q|| = ", norm q); println! ("||q1|| = ", norm q1); println! ("||q2|| = ", norm q2); println! (); println! ("-q = ", ~q); println! ("-q1 = ", ~q1); println! ("-q2 = ", ~q2); println! (); println! ("conj q = ", conj q); println! ("conj q1 = ", conj q1); println! ("conj q2 = ", conj q2); println! (); println! ("q + r = ", q + r); println! ("r + q = ", r + q); println! ("q1 + q2 = ", q1 + q2); println! (); println! ("q * r = ", q * r); println! ("r * q = ", r * q); println! ("q1 * q2 = ", q1 * q2); println! ("q2 * q1 = ", q2 * q1); println! ("((q1 * q2) = (q2 * q1)) is ", (q1 * q2) = (q2 * q1)) end //-------------------------------------------------------------------- Output: $ patscc -std=gnu2x -O2 quaternions_task.dats -lm && ./a.out
q = 1+2i+3j+4k
q1 = 2+3i+4j+5k
q2 = 3+4i+5j+6k

||q|| = 5.477226
||q1|| = 7.348469
||q2|| = 9.273618

-q = -1-2i-3j-4k
-q1 = -2-3i-4j-5k
-q2 = -3-4i-5j-6k

conj q = 1-2i-3j-4k
conj q1 = 2-3i-4j-5k
conj q2 = 3-4i-5j-6k

q + r = 8+2i+3j+4k
r + q = 8+2i+3j+4k
q1 + q2 = 5+7i+9j+11k

q * r = 7+14i+21j+28k
r * q = 7+14i+21j+28k
q1 * q2 = -56+16i+24j+26k
q2 * q1 = -56+18i+20j+28k
((q1 * q2) = (q2 * q1)) is false

## AutoHotkey

Works with: AutoHotkey_L

(AutoHotkey1.1+)

q  := [1, 2, 3, 4]
q1 := [2, 3, 4, 5]
q2 := [3, 4, 5, 6]
r := 7

MsgBox, % "q = " PrintQ(q)
. "nq1 = " PrintQ(q1)
. "nq2 = " PrintQ(q2)
. "nr = " r
. "nNorm(q) = " Norm(q)
. "nNegative(q) = " PrintQ(Negative(q))
. "nConjugate(q) = " PrintQ(Conjugate(q))
. "nq + r = " PrintQ(AddR(q, r))
. "nq1 + q2 = " PrintQ(AddQ(q1, q2))
. "nq2 + q1 = " PrintQ(AddQ(q2, q1))
. "nqr = " PrintQ(MulR(q, r))
. "nq1q2 = " PrintQ(MulQ(q1, q2))
. "nq2q1 = " PrintQ(MulQ(q2, q1))

Norm(q) {
return sqrt(q[1]**2 + q[2]**2 + q[3]**2 + q[4]**2)
}

Negative(q) {
a := []
for k, v in q
a[A_Index] := v * -1
return a
}

Conjugate(q) {
a := []
for k, v in q
a[A_Index] := v * (A_Index = 1 ? 1 : -1)
return a
}

a := []
for k, v in q
a[A_Index] := v + (A_Index = 1 ? r : 0)
return a
}

a := []
for k, v in q1
a[A_Index] := v + q2[A_Index]
return a
}

MulR(q, r) {
a := []
for k, v in q
a[A_Index] := v * r
return a
}

MulQ(q, u) {
a := []
, a[1] := q[1]*u[1] - q[2]*u[2] - q[3]*u[3] - q[4]*u[4]
, a[2] := q[1]*u[2] + q[2]*u[1] + q[3]*u[4] - q[4]*u[3]
, a[3] := q[1]*u[3] - q[2]*u[4] + q[3]*u[1] + q[4]*u[2]
, a[4] := q[1]*u[4] + q[2]*u[3] - q[3]*u[2] + q[4]*u[1]
return a
}

PrintQ(q, b="(") {
for k, v in q
b .= v (A_Index = q.MaxIndex() ? ")" : ", ")
return b
}

Output:
q = (1, 2, 3, 4)
q1 = (2, 3, 4, 5)
q2 = (3, 4, 5, 6)
r = 7
Norm(q) = 5.477226
Negative(q) = (-1, -2, -3, -4)
Conjugate(q) = (1, -2, -3, -4)
q + r = (8, 2, 3, 4)
q1 + q2 = (5, 7, 9, 11)
q2 + q1 = (5, 7, 9, 11)
qr = (7, 14, 21, 28)
q1q2 = (-56, 16, 24, 26)
q2q1 = (-56, 18, 20, 28)

## Axiom

Axiom has built-in support for quaternions.

qi := quatern$Quaternion(Integer); Type: ((Integer,Integer,Integer,Integer) -> Quaternion(Integer)) q := qi(1,2,3,4); Type: Quaternion(Integer) q1 := qi(2,3,4,5); Type: Quaternion(Integer) q2 := qi(3,4,5,6); Type: Quaternion(Integer) r : Integer := 7; Type: Integer sqrt norm q +--+ (6) \|30 Type: AlgebraicNumber -q (7) - 1 - 2i - 3j - 4k Type: Quaternion(Integer) conjugate q (8) 1 - 2i - 3j - 4k Type: Quaternion(Integer) r + q (9) 8 + 2i + 3j + 4k Type: Quaternion(Integer) q1 + q2 (10) 5 + 7i + 9j + 11k Type: Quaternion(Integer) q*r (11) 7 + 14i + 21j + 28k Type: Quaternion(Integer) r*q (12) 7 + 14i + 21j + 28k Type: Quaternion(Integer) q1*q2 ~= q2*q1 (13) true Type: Boolean ## BASIC ### BASIC256 Works with: BASIC256 version 2.0.0.11 dim q(4) dim q1(4) dim q2(4) q[0] = 1: q[1] = 2: q[2] = 3: q[3] = 4 q1[0] = 2: q1[1] = 3: q1[2] = 4: q1[3] = 5 q2[0] = 3: q2[1] = 4: q2[2] = 5: q2[3] = 6 r = 7 function printq(q) return "("+q[0]+", "+q[1]+", "+q[2]+", "+q[3]+")" end function function q_equal(q1, q2) return q1[0]=q2[0] and q1[1]=q2[1] and q1[2]=q2[2] and q1[3]=q2[3] end function function q_norm(q) return sqr(q[0]*q[0]+q[1]*q[1]+q[2]*q[2]+q[3]*q[3]) end function function q_neg(q) dim result[4] result[0] = -q[0] result[1] = -q[1] result[2] = -q[2] result[3] = -q[3] return result end function function q_conj(q) dim result[4] result[0] = q[0] result[1] = -q[1] result[2] = -q[2] result[3] = -q[3] return result end function function q_addreal(q, r) dim result[4] result[0] = q[0]+r result[1] = q[1] result[2] = q[2] result[3] = q[3] return result end function function q_add(q1, q2) dim result[4] result[0] = q1[0]+q2[0] result[1] = q1[1]+q2[1] result[2] = q1[2]+q2[2] result[3] = q1[3]+q2[3] return result end function function q_mulreal(q, r) dim result[4] result[0] = q[0]*r result[1] = q[1]*r result[2] = q[2]*r result[3] = q[3]*r return result end function function q_mul(q1, q2) dim result[4] result[0] = q1[0]*q2[0]-q1[1]*q2[1]-q1[2]*q2[2]-q1[3]*q2[3] result[1] = q1[0]*q2[1]+q1[1]*q2[0]+q1[2]*q2[3]-q1[3]*q2[2] result[2] = q1[0]*q2[2]-q1[1]*q2[3]+q1[2]*q2[0]+q1[3]*q2[1] result[3] = q1[0]*q2[3]+q1[1]*q2[2]-q1[2]*q2[1]+q1[3]*q2[0] return result end function print "q = ";printq(q) print "q1 = ";printq(q1) print "q2 = ";printq(q2) print "r = "; r print "norm(q) = "; q_norm(q) print "neg(q) = ";printq(q_neg(q)) print "conjugate(q) = ";printq(q_conj(q)) print "q+r = ";printq(q_addreal(q,r)) print "q1+q2 = ";printq(q_add(q1,q2)) print "qr = ";printq(q_mulreal(q,r)) print "q1q2 = ";printq(q_mul(q1,q2)) print "q2q1 = ";printq(q_mul(q2,q1)) Output: q = (1, 2, 3, 4) q1 = (2, 3, 4, 5) q2 = (3, 4, 5, 6) r = 7 norm(q) = 5.47722557505 neg(q) = (-1, -2, -3, -4) conjugate(q) = (1, -2, -3, -4) q+r = (8, 2, 3, 4) q1+q2 = (5, 7, 9, 11) qr = (7, 14, 21, 28) q1q2 = (-56, 16, 24, 26) q2q1 = (-56, 18, 20, 28)  ### BBC BASIC Although BBC BASIC doesn't have native support for quaternions its array arithmetic provides all of the required operations either directly or very straightforwardly.  DIM q(3), q1(3), q2(3), t(3) q() = 1, 2, 3, 4 q1() = 2, 3, 4, 5 q2() = 3, 4, 5, 6 r = 7 PRINT "q = " FNq_show(q()) PRINT "q1 = " FNq_show(q1()) PRINT "q2 = " FNq_show(q2()) PRINT "r = "; r PRINT "norm(q) = "; FNq_norm(q()) t() = q() : PROCq_neg(t()) : PRINT "neg(q) = " FNq_show(t()) t() = q() : PROCq_conj(t()) : PRINT "conjugate(q) = " FNq_show(t()) t() = q() : PROCq_addreal(t(),r) : PRINT "q + r = " FNq_show(t()) t() = q1() : PROCq_add(t(),q2()) : PRINT "q1 + q2 = " FNq_show(t()) t() = q2() : PROCq_add(t(),q1()) : PRINT "q2 + q1 = " FNq_show(t()) t() = q() : PROCq_mulreal(t(),r) : PRINT "qr = " FNq_show(t()) t() = q1() : PROCq_mul(t(),q2()) : PRINT "q1q2 = " FNq_show(t()) t() = q2() : PROCq_mul(t(),q1()) : PRINT "q2q1 = " FNq_show(t()) END DEF FNq_norm(q()) = MOD(q()) DEF PROCq_neg(q()) : q() *= -1 : ENDPROC DEF PROCq_conj(q()) : q() *= -1 : q(0) *= -1 : ENDPROC DEF PROCq_addreal(q(), r) : q(0) += r : ENDPROC DEF PROCq_add(q(), r()) : q() += r() : ENDPROC DEF PROCq_mulreal(q(), r) : q() *= r : ENDPROC DEF PROCq_mul(q(), r()) : LOCAL s() : DIM s(3,3) s() = r(0), -r(1), -r(2), -r(3), r(1), r(0), r(3), -r(2), \ \ r(2), -r(3), r(0), r(1), r(3), r(2), -r(1), r(0) q() = s() . q() ENDPROC DEF FNq_show(q()) : LOCAL i%, a$ : a$= "(" FOR i% = 0 TO 3 : a$ += STR$(q(i%)) + ", " : NEXT = LEFT$(LEFT$(a$)) + ")"

Output:
q = (1, 2, 3, 4)
q1 = (2, 3, 4, 5)
q2 = (3, 4, 5, 6)
r = 7
norm(q) = 5.47722558
neg(q) = (-1, -2, -3, -4)
conjugate(q) = (1, -2, -3, -4)
q + r = (8, 2, 3, 4)
q1 + q2 = (5, 7, 9, 11)
q2 + q1 = (5, 7, 9, 11)
qr = (7, 14, 21, 28)
q1q2 = (-56, 16, 24, 26)
q2q1 = (-56, 18, 20, 28)


## C

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <math.h>

typedef struct quaternion
{
double q[4];
} quaternion_t;

quaternion_t *quaternion_new(void)
{
return malloc(sizeof(quaternion_t));
}

quaternion_t *quaternion_new_set(double q1,
double q2,
double q3,
double q4)
{
quaternion_t *q = malloc(sizeof(quaternion_t));
if (q != NULL) {
q->q[0] = q1; q->q[1] = q2; q->q[2] = q3; q->q[3] = q4;
}
return q;
}

void quaternion_copy(quaternion_t *r, quaternion_t *q)
{
size_t i;

if (r == NULL || q == NULL) return;
for(i = 0; i < 4; i++) r->q[i] = q->q[i];
}

double quaternion_norm(quaternion_t *q)
{
size_t i;
double r = 0.0;

if (q == NULL) {
fprintf(stderr, "NULL quaternion in norm\n");
return 0.0;
}

for(i = 0; i < 4; i++) r += q->q[i] * q->q[i];
return sqrt(r);
}

void quaternion_neg(quaternion_t *r, quaternion_t *q)
{
size_t i;

if (q == NULL || r == NULL) return;
for(i = 0; i < 4; i++) r->q[i] = -q->q[i];
}

void quaternion_conj(quaternion_t *r, quaternion_t *q)
{
size_t i;

if (q == NULL || r == NULL) return;
r->q[0] = q->q[0];
for(i = 1; i < 4; i++) r->q[i] = -q->q[i];
}

void quaternion_add_d(quaternion_t *r, quaternion_t *q, double d)
{
if (q == NULL || r == NULL) return;
quaternion_copy(r, q);
r->q[0] += d;
}

void quaternion_add(quaternion_t *r, quaternion_t *a, quaternion_t *b)
{
size_t i;

if (r == NULL || a == NULL || b == NULL) return;
for(i = 0; i < 4; i++) r->q[i] = a->q[i] + b->q[i];
}

void quaternion_mul_d(quaternion_t *r, quaternion_t *q, double d)
{
size_t i;

if (r == NULL || q == NULL) return;
for(i = 0; i < 4; i++) r->q[i] = q->q[i] * d;
}

bool quaternion_equal(quaternion_t *a, quaternion_t *b)
{
size_t i;

for(i = 0; i < 4; i++) if (a->q[i] != b->q[i]) return false;
return true;
}

#define A(N) (a->q[(N)])
#define B(N) (b->q[(N)])
#define R(N) (r->q[(N)])
void quaternion_mul(quaternion_t *r, quaternion_t *a, quaternion_t *b)
{
size_t i;
double ri = 0.0;

if (r == NULL || a == NULL || b == NULL) return;
R(0) = A(0)*B(0) - A(1)*B(1) - A(2)*B(2) - A(3)*B(3);
R(1) = A(0)*B(1) + A(1)*B(0) + A(2)*B(3) - A(3)*B(2);
R(2) = A(0)*B(2) - A(1)*B(3) + A(2)*B(0) + A(3)*B(1);
R(3) = A(0)*B(3) + A(1)*B(2) - A(2)*B(1) + A(3)*B(0);
}
#undef A
#undef B
#undef R

void quaternion_print(quaternion_t *q)
{
if (q == NULL) return;
printf("(%lf, %lf, %lf, %lf)\n",
q->q[0], q->q[1], q->q[2], q->q[3]);
}

int main()
{
size_t i;
double d = 7.0;
quaternion_t *q[3];
quaternion_t *r  = quaternion_new();

quaternion_t *qd = quaternion_new_set(7.0, 0.0, 0.0, 0.0);
q[0] = quaternion_new_set(1.0, 2.0, 3.0, 4.0);
q[1] = quaternion_new_set(2.0, 3.0, 4.0, 5.0);
q[2] = quaternion_new_set(3.0, 4.0, 5.0, 6.0);

printf("r = %lf\n", d);

for(i = 0; i < 3; i++) {
printf("q[%u] = ", i);
quaternion_print(q[i]);
printf("abs q[%u] = %lf\n", i, quaternion_norm(q[i]));
}

printf("-q[0] = ");
quaternion_neg(r, q[0]);
quaternion_print(r);

printf("conj q[0] = ");
quaternion_conj(r, q[0]);
quaternion_print(r);

printf("q[1] + q[2] = ");
quaternion_print(r);

printf("q[2] + q[1] = ");
quaternion_print(r);

printf("q[0] * r = ");
quaternion_mul_d(r, q[0], d);
quaternion_print(r);

printf("q[0] * (r, 0, 0, 0) = ");
quaternion_mul(r, q[0], qd);
quaternion_print(r);

printf("q[1] * q[2] = ");
quaternion_mul(r, q[1], q[2]);
quaternion_print(r);

printf("q[2] * q[1] = ");
quaternion_mul(r, q[2], q[1]);
quaternion_print(r);

free(q[0]); free(q[1]); free(q[2]); free(r);
return EXIT_SUCCESS;
}


## C#

using System;

struct Quaternion : IEquatable<Quaternion>
{
public readonly double A, B, C, D;

public Quaternion(double a, double b, double c, double d)
{
this.A = a;
this.B = b;
this.C = c;
this.D = d;
}

public double Norm()
{
return Math.Sqrt(A * A + B * B + C * C + D * D);
}

public static Quaternion operator -(Quaternion q)
{
return new Quaternion(-q.A, -q.B, -q.C, -q.D);
}

public Quaternion Conjugate()
{
return new Quaternion(A, -B, -C, -D);
}

// implicit conversion takes care of real*quaternion and real+quaternion
public static implicit operator Quaternion(double d)
{
return new Quaternion(d, 0, 0, 0);
}

public static Quaternion operator +(Quaternion q1, Quaternion q2)
{
return new Quaternion(q1.A + q2.A, q1.B + q2.B, q1.C + q2.C, q1.D + q2.D);
}

public static Quaternion operator *(Quaternion q1, Quaternion q2)
{
return new Quaternion(
q1.A * q2.A - q1.B * q2.B - q1.C * q2.C - q1.D * q2.D,
q1.A * q2.B + q1.B * q2.A + q1.C * q2.D - q1.D * q2.C,
q1.A * q2.C - q1.B * q2.D + q1.C * q2.A + q1.D * q2.B,
q1.A * q2.D + q1.B * q2.C - q1.C * q2.B + q1.D * q2.A);
}

public static bool operator ==(Quaternion q1, Quaternion q2)
{
return q1.A == q2.A && q1.B == q2.B && q1.C == q2.C && q1.D == q2.D;
}

public static bool operator !=(Quaternion q1, Quaternion q2)
{
return !(q1 == q2);
}

#region Object Members

public override bool Equals(object obj)
{
if (obj is Quaternion)
return Equals((Quaternion)obj);

return false;
}

public override int GetHashCode()
{
return A.GetHashCode() ^ B.GetHashCode() ^ C.GetHashCode() ^ D.GetHashCode();
}

public override string ToString()
{
return string.Format("Q({0}, {1}, {2}, {3})", A, B, C, D);
}

#endregion

#region IEquatable<Quaternion> Members

public bool Equals(Quaternion other)
{
return other == this;
}

#endregion
}


Demonstration:

using System;

static class Program
{
static void Main(string[] args)
{
Quaternion q = new Quaternion(1, 2, 3, 4);
Quaternion q1 = new Quaternion(2, 3, 4, 5);
Quaternion q2 = new Quaternion(3, 4, 5, 6);
double r = 7;

Console.WriteLine("q = {0}", q);
Console.WriteLine("q1 = {0}", q1);
Console.WriteLine("q2 = {0}", q2);
Console.WriteLine("r = {0}", r);

Console.WriteLine("q.Norm() = {0}", q.Norm());
Console.WriteLine("q1.Norm() = {0}", q1.Norm());
Console.WriteLine("q2.Norm() = {0}", q2.Norm());

Console.WriteLine("-q = {0}", -q);
Console.WriteLine("q.Conjugate() = {0}", q.Conjugate());

Console.WriteLine("q + r = {0}", q + r);
Console.WriteLine("q1 + q2 = {0}", q1 + q2);
Console.WriteLine("q2 + q1 = {0}", q2 + q1);

Console.WriteLine("q * r = {0}", q * r);
Console.WriteLine("q1 * q2 = {0}", q1 * q2);
Console.WriteLine("q2 * q1 = {0}", q2 * q1);

Console.WriteLine("q1*q2 {0} q2*q1", (q1 * q2) == (q2 * q1) ? "==" : "!=");
}
}

Output:
q = Q(1, 2, 3, 4)
q1 = Q(2, 3, 4, 5)
q2 = Q(3, 4, 5, 6)
r = 7
q.Norm() = 5.47722557505166
q1.Norm() = 7.34846922834953
q2.Norm() = 9.2736184954957
-q = Q(-1, -2, -3, -4)
q.Conjugate() = Q(1, -2, -3, -4)
q + r = Q(8, 2, 3, 4)
q1 + q2 = Q(5, 7, 9, 11)
q2 + q1 = Q(5, 7, 9, 11)
q * r = Q(7, 14, 21, 28)
q1 * q2 = Q(-56, 16, 24, 26)
q2 * q1 = Q(-56, 18, 20, 28)
q1*q2 != q2*q1

## C++

This example uses templates to provide the underlying data-type, and includes several extra functions and constructors that often come up when using quaternions.

#include <iostream>
using namespace std;

template<class T = double>
class Quaternion
{
public:
T w, x, y, z;

// Numerical constructor
Quaternion(const T &w, const T &x, const T &y, const T &z): w(w), x(x), y(y), z(z) {};
Quaternion(const T &x, const T &y, const T &z): w(T()), x(x), y(y), z(z) {}; // For 3-rotations
Quaternion(const T &r): w(r), x(T()), y(T()), z(T()) {};
Quaternion(): w(T()), x(T()), y(T()), z(T()) {};

// Copy constructor and assignment
Quaternion(const Quaternion &q): w(q.w), x(q.x), y(q.y), z(q.z) {};
Quaternion& operator=(const Quaternion &q) { w=q.w; x=q.x; y=q.y; z=q.z; return *this; }

// Unary operators
Quaternion operator-() const { return Quaternion(-w, -x, -y, -z); }
Quaternion operator~() const { return Quaternion(w, -x, -y, -z); } // Conjugate

// Norm-squared. SQRT would have to be made generic to be used here
T normSquared() const { return w*w + x*x + y*y + z*z; }

// In-place operators
Quaternion& operator+=(const T &r)
{ w += r; return *this; }
Quaternion& operator+=(const Quaternion &q)
{ w += q.w; x += q.x; y += q.y; z += q.z; return *this; }

Quaternion& operator-=(const T &r)
{ w -= r; return *this; }
Quaternion& operator-=(const Quaternion &q)
{ w -= q.w; x -= q.x; y -= q.y; z -= q.z; return *this; }

Quaternion& operator*=(const T &r)
{ w *= r; x *= r; y *= r; z *= r; return *this; }
Quaternion& operator*=(const Quaternion &q)
{
T oldW(w), oldX(x), oldY(y), oldZ(z);
w = oldW*q.w - oldX*q.x - oldY*q.y - oldZ*q.z;
x = oldW*q.x + oldX*q.w + oldY*q.z - oldZ*q.y;
y = oldW*q.y + oldY*q.w + oldZ*q.x - oldX*q.z;
z = oldW*q.z + oldZ*q.w + oldX*q.y - oldY*q.x;
return *this;
}

Quaternion& operator/=(const T &r)
{ w /= r; x /= r; y /= r; z /= r; return *this; }
Quaternion& operator/=(const Quaternion &q)
{
T oldW(w), oldX(x), oldY(y), oldZ(z), n(q.normSquared());
w = (oldW*q.w + oldX*q.x + oldY*q.y + oldZ*q.z) / n;
x = (oldX*q.w - oldW*q.x + oldY*q.z - oldZ*q.y) / n;
y = (oldY*q.w - oldW*q.y + oldZ*q.x - oldX*q.z) / n;
z = (oldZ*q.w - oldW*q.z + oldX*q.y - oldY*q.x) / n;
return *this;
}

// Binary operators based on in-place operators
Quaternion operator+(const T &r) const { return Quaternion(*this) += r; }
Quaternion operator+(const Quaternion &q) const { return Quaternion(*this) += q; }
Quaternion operator-(const T &r) const { return Quaternion(*this) -= r; }
Quaternion operator-(const Quaternion &q) const { return Quaternion(*this) -= q; }
Quaternion operator*(const T &r) const { return Quaternion(*this) *= r; }
Quaternion operator*(const Quaternion &q) const { return Quaternion(*this) *= q; }
Quaternion operator/(const T &r) const { return Quaternion(*this) /= r; }
Quaternion operator/(const Quaternion &q) const { return Quaternion(*this) /= q; }

// Comparison operators, as much as they make sense
bool operator==(const Quaternion &q) const
{ return (w == q.w) && (x == q.x) && (y == q.y) && (z == q.z); }
bool operator!=(const Quaternion &q) const { return !operator==(q); }

// The operators above allow quaternion op real. These allow real op quaternion.
// Uses the above where appropriate.
template<class T> friend Quaternion<T> operator+(const T &r, const Quaternion<T> &q);
template<class T> friend Quaternion<T> operator-(const T &r, const Quaternion<T> &q);
template<class T> friend Quaternion<T> operator*(const T &r, const Quaternion<T> &q);
template<class T> friend Quaternion<T> operator/(const T &r, const Quaternion<T> &q);

// Allows cout << q
template<class T> friend ostream& operator<<(ostream &io, const Quaternion<T> &q);
};

// Friend functions need to be outside the actual class definition
template<class T>
Quaternion<T> operator+(const T &r, const Quaternion<T> &q)
{ return q+r; }

template<class T>
Quaternion<T> operator-(const T &r, const Quaternion<T> &q)
{ return Quaternion<T>(r-q.w, q.x, q.y, q.z); }

template<class T>
Quaternion<T> operator*(const T &r, const Quaternion<T> &q)
{ return q*r; }

template<class T>
Quaternion<T> operator/(const T &r, const Quaternion<T> &q)
{
T n(q.normSquared());
return Quaternion(r*q.w/n, -r*q.x/n, -r*q.y/n, -r*q.z/n);
}

template<class T>
ostream& operator<<(ostream &io, const Quaternion<T> &q)
{
io << q.w;
(q.x < T()) ? (io << " - " << (-q.x) << "i") : (io << " + " << q.x << "i");
(q.y < T()) ? (io << " - " << (-q.y) << "j") : (io << " + " << q.y << "j");
(q.z < T()) ? (io << " - " << (-q.z) << "k") : (io << " + " << q.z << "k");
return io;
}


Test program:

int main()
{
Quaternion<> q0(1, 2, 3, 4);
Quaternion<> q1(2, 3, 4, 5);
Quaternion<> q2(3, 4, 5, 6);
double r = 7;

cout << "q0:      " << q0 << endl;
cout << "q1:      " << q1 << endl;
cout << "q2:      " << q2 << endl;
cout << "r:       " << r << endl;
cout << endl;
cout << "-q0:     " << -q0 << endl;
cout << "~q0:     " << ~q0 << endl;
cout << endl;
cout << "r * q0:  " << r*q0 << endl;
cout << "r + q0:  " << r+q0 << endl;
cout << "q0 / r:  " << q0/r << endl;
cout << "q0 - r:  " << q0-r << endl;
cout << endl;
cout << "q0 + q1: " << q0+q1 << endl;
cout << "q0 - q1: " << q0-q1 << endl;
cout << "q0 * q1: " << q0*q1 << endl;
cout << "q0 / q1: " << q0/q1 << endl;
cout << endl;
cout << "q0 * ~q0:     " << q0*~q0 << endl;
cout << "q0 + q1*q2:   " << q0+q1*q2 << endl;
cout << "(q0 + q1)*q2: " << (q0+q1)*q2 << endl;
cout << "q0*q1*q2:     " << q0*q1*q2 << endl;
cout << "(q0*q1)*q2:   " << (q0*q1)*q2 << endl;
cout << "q0*(q1*q2):   " << q0*(q1*q2) << endl;
cout << endl;
cout << "||q0||:  " << sqrt(q0.normSquared()) << endl;
cout << endl;
cout << "q0*q1 - q1*q0: " << (q0*q1 - q1*q0) << endl;

// Other base types
Quaternion<int> q5(2), q6(3);
cout << endl << q5*q6 << endl;
}

Output:
q0:      1 + 2i + 3j + 4k
q1:      2 + 3i + 4j + 5k
q2:      3 + 4i + 5j + 6k
r:       7

-q0:     -1 - 2i - 3j - 4k
~q0:     1 - 2i - 3j - 4k

r * q0:  7 + 14i + 21j + 28k
r + q0:  8 + 2i + 3j + 4k
q0 / r:  0.142857 + 0.285714i + 0.428571j + 0.571429k
q0 - r:  -6 + 2i + 3j + 4k

q0 + q1: 3 + 5i + 7j + 9k
q0 - q1: -1 - 1i - 1j - 1k
q0 * q1: -36 + 6i + 12j + 12k
q0 / q1: 0.740741 + 0i + 0.0740741j + 0.037037k

q0 * ~q0:     30 + 0i + 0j + 0k
q0 + q1*q2:   -55 + 18i + 27j + 30k
(q0 + q1)*q2: -100 + 24i + 42j + 42k
q0*q1*q2:     -264 - 114i - 132j - 198k
(q0*q1)*q2:   -264 - 114i - 132j - 198k
q0*(q1*q2):   -264 - 114i - 132j - 198k

||q0||:  5.47723

q0*q1 - q1*q0: 0 - 2i + 4j - 2k

6 + 0i + 0j + 0k


## CLU

quat = cluster is make, minus, norm, conj, add, addr, mul, mulr,
equal, get_a, get_b, get_c, get_d, q_form
rep = struct[a,b,c,d: real]

make = proc (a,b,c,d: real) returns (cvt)
return (rep${a:a, b:b, c:c, d:d}) end make minus = proc (q: cvt) returns (cvt) return (down(make(-q.a, -q.b, -q.c, -q.d))) end minus norm = proc (q: cvt) returns (real) return ((q.a**2.0 + q.b**2.0 + q.c**2.0 + q.d**2.0) ** 0.5) end norm conj = proc (q: cvt) returns (cvt) return (down(make(q.a, -q.b, -q.c, q.d))) end conj add = proc (q1, q2: cvt) returns (cvt) return (down(make(q1.a+q2.a, q1.b+q2.b, q1.c+q2.c, q1.d+q2.d))) end add addr = proc (q: cvt, r: real) returns (cvt) return (down(make(q.a+r, q.b+r, q.c+r, q.d+r))) end addr mul = proc (q1, q2: cvt) returns (cvt) a: real := q1.a*q2.a - q1.b*q2.b - q1.c*q2.c - q1.d*q2.d b: real := q1.a*q2.b + q1.b*q2.a + q1.c*q2.d - q1.d*q2.c c: real := q1.a*q2.c - q1.b*q2.d + q1.c*q2.a + q1.d*q2.b d: real := q1.a*q2.d + q1.b*q2.c - q1.c*q2.b + q1.d*q2.a return (down(make(a,b,c,d))) end mul mulr = proc (q: cvt, r: real) returns (cvt) return (down(make(q.a*r, q.b*r, q.c*r, q.d*r))) end mulr equal = proc (q1, q2: cvt) returns (bool) return (q1.a = q2.a & q1.b = q2.b & q1.c = q2.c & q1.d = q2.d) end equal get_a = proc (q: cvt) returns (real) return (q.a) end get_a get_b = proc (q: cvt) returns (real) return (q.b) end get_b get_c = proc (q: cvt) returns (real) return (q.c) end get_c get_d = proc (q: cvt) returns (real) return (q.d) end get_d q_form = proc (q: cvt, a, b: int) returns (string) return ( f_form(q.a, a, b) || " + " || f_form(q.b, a, b) || "i + " || f_form(q.c, a, b) || "j + " || f_form(q.d, a, b) || "k" ) end q_form end quat start_up = proc () po: stream := stream$primary_output()

q0: quat := quat$make(1.0, 2.0, 3.0, 4.0) q1: quat := quat$make(2.0, 3.0, 4.0, 5.0)
q2: quat := quat$make(3.0, 4.0, 5.0, 6.0) r: real := 7.0 stream$putl(po, "      q0 = " || quat$q_form(q0, 3, 3)) stream$putl(po, "      q1 = " || quat$q_form(q1, 3, 3)) stream$putl(po, "      q2 = " || quat$q_form(q2, 3, 3)) stream$putl(po, "       r = " || f_form(r, 3, 3))
stream$putl(po, "") stream$putl(po, "norm(q0) = " || f_form(quat$norm(q0), 3, 3)) stream$putl(po, "     -q0 = " || quat$q_form(-q0, 3, 3)) stream$putl(po, "conj(q0) = " || quat$q_form(quat$conj(q0), 3, 3))
stream$putl(po, " q0 + r = " || quat$q_form(quat$addr(q0, r), 3, 3)) stream$putl(po, " q1 + q2 = " || quat$q_form(q1 + q2, 3, 3)) stream$putl(po, "  q0 * r = " || quat$q_form(quat$mulr(q0, r), 3, 3))
stream$putl(po, " q1 * q2 = " || quat$q_form(q1 * q2, 3, 3))
stream$putl(po, " q2 * q1 = " || quat$q_form(q2 * q1, 3, 3))

if q1*q2 ~= q2*q1 then stream$putl(po, "q1 * q2 ~= q2 * q1") end end start_up Output:  q0 = 1.000 + 2.000i + 3.000j + 4.000k q1 = 2.000 + 3.000i + 4.000j + 5.000k q2 = 3.000 + 4.000i + 5.000j + 6.000k r = 7.000 norm(q0) = 5.477 -q0 = -1.000 + -2.000i + -3.000j + -4.000k conj(q0) = 1.000 + -2.000i + -3.000j + 4.000k q0 + r = 8.000 + 9.000i + 10.000j + 11.000k q1 + q2 = 5.000 + 7.000i + 9.000j + 11.000k q0 * r = 7.000 + 14.000i + 21.000j + 28.000k q1 * q2 = -56.000 + 16.000i + 24.000j + 26.000k q2 * q1 = -56.000 + 18.000i + 20.000j + 28.000k q1 * q2 ~= q2 * q1 ## Common Lisp (defclass quaternion () ((a :accessor q-a :initarg :a :type real) (b :accessor q-b :initarg :b :type real) (c :accessor q-c :initarg :c :type real) (d :accessor q-d :initarg :d :type real)) (:default-initargs :a 0 :b 0 :c 0 :d 0)) (defun make-q (&optional (a 0) (b 0) (c 0) (d 0)) (make-instance 'quaternion :a a :b b :c c :d d)) (defgeneric sum (x y)) (defmethod sum ((x quaternion) (y quaternion)) (make-q (+ (q-a x) (q-a y)) (+ (q-b x) (q-b y)) (+ (q-c x) (q-c y)) (+ (q-d x) (q-d y)))) (defmethod sum ((x quaternion) (y real)) (make-q (+ (q-a x) y) (q-b x) (q-c x) (q-d x))) (defmethod sum ((x real) (y quaternion)) (make-q (+ (q-a y) x) (q-b y) (q-c y) (q-d y))) (defgeneric sub (x y)) (defmethod sub ((x quaternion) (y quaternion)) (make-q (- (q-a x) (q-a y)) (- (q-b x) (q-b y)) (- (q-c x) (q-c y)) (- (q-d x) (q-d y)))) (defmethod sub ((x quaternion) (y real)) (make-q (- (q-a x) y) (q-b x) (q-c x) (q-d x))) (defmethod sub ((x real) (y quaternion)) (make-q (- (q-a y) x) (q-b y) (q-c y) (q-d y))) (defgeneric mul (x y)) (defmethod mul ((x quaternion) (y real)) (make-q (* (q-a x) y) (* (q-b x) y) (* (q-c x) y) (* (q-d x) y))) (defmethod mul ((x real) (y quaternion)) (make-q (* (q-a y) x) (* (q-b y) x) (* (q-c y) x) (* (q-d y) x))) (defmethod mul ((x quaternion) (y quaternion)) (make-q (- (* (q-a x) (q-a y)) (* (q-b x) (q-b y)) (* (q-c x) (q-c y)) (* (q-d x) (q-d y))) (- (+ (* (q-a x) (q-b y)) (* (q-b x) (q-a y)) (* (q-c x) (q-d y))) (* (q-d x) (q-c y))) (- (+ (* (q-a x) (q-c y)) (* (q-c x) (q-a y)) (* (q-d x) (q-b y))) (* (q-b x) (q-d y))) (- (+ (* (q-a x) (q-d y)) (* (q-b x) (q-c y)) (* (q-d x) (q-a y))) (* (q-c x) (q-b y))))) (defmethod norm ((x quaternion)) (+ (sqrt (q-a x)) (sqrt (q-b x)) (sqrt (q-c x)) (sqrt (q-d x)))) (defmethod print-object ((x quaternion) stream) (format stream "~@f~@fi~@fj~@fk" (q-a x) (q-b x) (q-c x) (q-d x))) (defvar q (make-q 0 1 0 0)) (defvar q1 (make-q 0 0 1 0)) (defvar q2 (make-q 0 0 0 1)) (defvar r 7) (format t "q+q1+q2 = ~a~&" (reduce #'sum (list q q1 q2))) (format t "r*(q+q1+q2) = ~a~&" (mul r (reduce #'sum (list q q1 q2)))) (format t "q*q1*q2 = ~a~&" (reduce #'mul (list q q1 q2))) (format t "q-q1-q2 = ~a~&" (reduce #'sub (list q q1 q2)))  Output: q+q1+q2 = +0.0+1.0i+1.0j+1.0k r*(q+q1+q2) = +0.0+7.0i+7.0j+7.0k q*q1*q2 = -1.0+0.0i+0.0j+0.0k q-q1-q2 = +0.0+1.0i-1.0j-1.0k  ## Crystal Translation of: Rust and Ruby class Quaternion property a, b, c, d def initialize(@a : Int64, @b : Int64, @c : Int64, @d : Int64) end def norm; Math.sqrt(a**2 + b**2 + c**2 + d**2) end def conj; Quaternion.new(a, -b, -c, -d) end def +(n) Quaternion.new(a + n, b, c, d) end def -(n) Quaternion.new(a - n, b, c, d) end def -() Quaternion.new(-a, -b, -c, -d) end def *(n) Quaternion.new(a * n, b * n, c * n, d * n) end def ==(rhs : Quaternion) self.to_s == rhs.to_s end def +(rhs : Quaternion) Quaternion.new(a + rhs.a, b + rhs.b, c + rhs.c, d + rhs.d) end def -(rhs : Quaternion) Quaternion.new(a - rhs.a, b - rhs.b, c - rhs.c, d - rhs.d) end def *(rhs : Quaternion) Quaternion.new( a * rhs.a - b * rhs.b - c * rhs.c - d * rhs.d, a * rhs.b + b * rhs.a + c * rhs.d - d * rhs.c, a * rhs.c - b * rhs.d + c * rhs.a + d * rhs.b, a * rhs.d + b * rhs.c - c * rhs.b + d * rhs.a) end def to_s(io : IO) io << "(#{a} #{sgn(b)}i #{sgn(c)}j #{sgn(d)}k)\n" end private def sgn(n) n.sign|1 == 1 ? "+ #{n}" : "- #{n.abs}" end end struct Number def +(rhs : Quaternion) Quaternion.new(rhs.a + self, rhs.b, rhs.c, rhs.d) end def -(rhs : Quaternion) Quaternion.new(-rhs.a + self, -rhs.b, -rhs.c, -rhs.d) end def *(rhs : Quaternion) Quaternion.new(rhs.a * self, rhs.b * self, rhs.c * self, rhs.d * self) end end q0 = Quaternion.new(a: 1, b: 2, c: 3, d: 4) q1 = Quaternion.new(2, 3, 4, 5) q2 = Quaternion.new(3, 4, 5, 6) r = 7 puts "q0 = #{q0}" puts "q1 = #{q1}" puts "q2 = #{q2}" puts "r = #{r}" puts puts "normal of q0 = #{q0.norm}" puts "-q0 = #{-q0}" puts "conjugate of q0 = #{q0.conj}" puts "q0 * (conjugate of q0) = #{q0 * q0.conj}" puts "(conjugate of q0) * q0 = #{q0.conj * q0}" puts puts "r + q0 = #{r + q0}" puts "q0 + r = #{q0 + r}" puts puts " q0 - r = #{q0 - r}" puts "-q0 - r = #{-q0 - r}" puts " r - q0 = #{r - q0}" puts "-q0 + r = #{-q0 + r}" puts puts "r * q0 = #{r * q0}" puts "q0 * r = #{q0 * r}" puts puts "q0 + q1 = #{q0 + q1}" puts "q0 - q1 = #{q2 - q1}" puts "q0 * q1 = #{q0 * q1}" puts puts " q0 + q1 * q2 = #{q0 + q1 * q2}" puts "(q0 + q1) * q2 = #{(q0 + q1) * q2}" puts puts " q0 * q1 * q2 = #{q0 * q1 * q2}" puts "(q0 * q1) * q2 = #{(q0 * q1) * q2}" puts " q0 * (q1 * q2) = #{q0 * (q1 * q2)}" puts puts "q1 * q2 = #{q1 * q2}" puts "q2 * q1 = #{q2 * q1}" puts puts "q1 * q2 != q2 * q1 => #{(q1 * q2) != (q2 * q1)}" puts "q1 * q2 == q2 * q1 => #{(q1 * q2) == (q2 * q1)}"  Output: q0 = (1 + 2i + 3j + 4k) q1 = (2 + 3i + 4j + 5k) q2 = (3 + 4i + 5j + 6k) r = 7 normal of q0 = 5.477225575051661 -q0 = (-1 - 2i - 3j - 4k) conjugate of q0 = (1 - 2i - 3j - 4k) q0 * (conjugate of q0) = (30 + 0i + 0j + 0k) (conjugate of q0) * q0 = (30 + 0i + 0j + 0k) r + q0 = (8 + 2i + 3j + 4k) q0 + r = (8 + 2i + 3j + 4k) q0 - r = (-6 + 2i + 3j + 4k) -q0 - r = (-8 - 2i - 3j - 4k) r - q0 = (6 - 2i - 3j - 4k) -q0 + r = (6 - 2i - 3j - 4k) r * q0 = (7 + 14i + 21j + 28k) q0 * r = (7 + 14i + 21j + 28k) q0 + q1 = (3 + 5i + 7j + 9k) q0 - q1 = (1 + 1i + 1j + 1k) q0 * q1 = (-36 + 6i + 12j + 12k) q0 + q1 * q2 = (-55 + 18i + 27j + 30k) (q0 + q1) * q2 = (-100 + 24i + 42j + 42k) q0 * q1 * q2 = (-264 - 114i - 132j - 198k) (q0 * q1) * q2 = (-264 - 114i - 132j - 198k) q0 * (q1 * q2) = (-264 - 114i - 132j - 198k) q1 * q2 = (-56 + 16i + 24j + 26k) q2 * q1 = (-56 + 18i + 20j + 28k) q1 * q2 != q2 * q1 => true q1 * q2 == q2 * q1 => false ## D import std.math, std.numeric, std.traits, std.conv, std.complex; struct Quat(T) if (isFloatingPoint!T) { alias CT = Complex!T; union { struct { T re, i, j, k; } // Default init to NaN. struct { CT x, y; } struct { T[4] vector; } } string toString() const pure /*nothrow*/ @safe { return vector.text; } @property T norm2() const pure nothrow @safe @nogc { /// Norm squared. return re ^^ 2 + i ^^ 2 + j ^^ 2 + k ^^ 2; } @property T abs() const pure nothrow @safe @nogc { /// Norm. return sqrt(norm2); } @property T arg() const pure nothrow @safe @nogc { /// Theta. return acos(re / abs); // this may be incorrect... } @property Quat!T conj() const pure nothrow @safe @nogc { /// Conjugate. return Quat!T(re, -i, -j, -k); } @property Quat!T recip() const pure nothrow @safe @nogc { /// Reciprocal. return Quat!T(re / norm2, -i / norm2, -j / norm2, -k / norm2); } @property Quat!T pureim() const pure nothrow @safe @nogc { /// Pure imagery. return Quat!T(0, i, j, k); } @property Quat!T versor() const pure nothrow @safe @nogc { /// Unit versor. return this / abs; } /// Unit versor of imagery part. @property Quat!T iversor() const pure nothrow @safe @nogc { return pureim / pureim.abs; } /// Assignment. Quat!T opAssign(U : T)(Quat!U z) pure nothrow @safe @nogc { x = z.x; y = z.y; return this; } Quat!T opAssign(U : T)(Complex!U c) pure nothrow @safe @nogc { x = c; y = 0; return this; } Quat!T opAssign(U : T)(U r) pure nothrow @safe @nogc if (isNumeric!U) { re = r; i = 0; y = 0; return this; } /// Test for equal, not ordered so no opCmp. bool opEquals(U : T)(Quat!U z) const pure nothrow @safe @nogc { return re == z.re && i == z.i && j == z.j && k == z.k; } bool opEquals(U : T)(Complex!U c) const pure nothrow @safe @nogc { return re == c.re && i == c.im && j == 0 && k == 0; } bool opEquals(U : T)(U r) const pure nothrow @safe @nogc if (isNumeric!U) { return re == r && i == 0 && j == 0 && k == 0; } /// Unary op. Quat!T opUnary(string op)() const pure nothrow @safe @nogc if (op == "+") { return this; } Quat!T opUnary(string op)() const pure nothrow @safe @nogc if (op == "-") { return Quat!T(-re, -i, -j, -k); } /// Binary op, Quaternion on left of op. Quat!(CommonType!(T,U)) opBinary(string op, U)(Quat!U z) const pure nothrow @safe @nogc { alias typeof(return) C; static if (op == "+" ) { return C(re + z.re, i + z.i, j + z.j, k + z.k); } else static if (op == "-") { return C(re - z.re, i - z.i, j - z.j, k - z.k); } else static if (op == "*") { return C(re * z.re - i * z.i - j * z.j - k * z.k, re * z.i + i * z.re + j * z.k - k * z.j, re * z.j - i * z.k + j * z.re + k * z.i, re * z.k + i * z.j - j * z.i + k * z.re); } else static if (op == "/") { return this * z.recip; } } /// Extend complex to quaternion. Quat!(CommonType!(T,U)) opBinary(string op, U)(Complex!U c) const pure nothrow @safe @nogc { return opBinary!op(typeof(return)(c.re, c.im, 0, 0)); } /// For scalar. Quat!(CommonType!(T,U)) opBinary(string op, U)(U r) const pure nothrow @safe @nogc if (isNumeric!U) { alias typeof(return) C; static if (op == "+" ) { return C(re + r, i, j, k); } else static if (op == "-") { return C(re - r, i, j, k); } else static if (op == "*") { return C(re * r, i * r, j * r, k * r); } else static if (op == "/") { return C(re / r, i / r, j / r, k / r); } else static if (op == "^^") { return pow(r); } } /// Power function. Quat!(CommonType!(T,U)) pow(U)(U r) const pure nothrow @safe @nogc if (isNumeric!U) { return (abs^^r) * exp(r * iversor * arg); } /// Handle binary op if Quaternion on right of op and left is /// not quaternion. Quat!(CommonType!(T,U)) opBinaryRight(string op, U)(Complex!U c) const pure nothrow @safe @nogc { alias typeof(return) C; auto w = C(c.re, c.im, 0, 0); return w.opBinary!(op)(this); } Quat!(CommonType!(T,U)) opBinaryRight(string op, U)(U r) const pure nothrow @safe @nogc if (isNumeric!U) { alias typeof(return) C; static if (op == "+" || op == "*") { return opBinary!op(r); } else static if (op == "-") { return C(r - re , -i, -j, -k); } else static if (op == "/") { auto w = C(re, i, j, k); return w.recip * r; } } } HT exp(HT)(HT z) pure nothrow @safe @nogc if (is(HT T == Quat!T)) { immutable inorm = z.pureim.abs; return std.math.exp(z.re) * (cos(inorm) + z.iversor * sin(inorm)); } HT log(HT)(HT z) pure nothrow @safe @nogc if (is(HT T == Quat!T)) { return std.math.log(z.abs) + z.iversor * acos(z.re / z.abs); } void main() @safe { // Demo code. import std.stdio; alias QR = Quat!real; enum real r = 7.0; immutable QR q = QR(2, 3, 4, 5), q1 = QR(2, 3, 4, 5), q2 = QR(3, 4, 5, 6); writeln("1. q - norm: ", q.abs); writeln("2. q - negative: ", -q); writeln("3. q - conjugate: ", q.conj); writeln("4. r + q: ", r + q); writeln(" q + r: ", q + r); writeln("5. q1 + q2: ", q1 + q2); writeln("6. r * q: ", r * q); writeln(" q * r: ", q * r); writeln("7. q1 * q2: ", q1 * q2); writeln(" q2 * q1: ", q2 * q1); writeln("8. q1 * q2 != q2 * Q1 ? ", q1 * q2 != q2 * q1); immutable QR i = QR(0, 1, 0, 0), j = QR(0, 0, 1, 0), k = QR(0, 0, 0, 1); writeln("9.1 i * i: ", i * i); writeln(" J * j: ", j * j); writeln(" k * k: ", k * k); writeln(" i * j * k: ", i * j * k); writeln("9.2 q1 / q2: ", q1 / q2); writeln("9.3 q1 / q2 * q2: ", q1 / q2 * q2); writeln(" q2 * q1 / q2: ", q2 * q1 / q2); writeln("9.4 exp(pi * i): ", exp(PI * i)); writeln(" exp(pi * j): ", exp(PI * j)); writeln(" exp(pi * k): ", exp(PI * k)); writeln(" exp(q): ", exp(q)); writeln(" log(q): ", log(q)); writeln(" exp(log(q)): ", exp(log(q))); writeln(" log(exp(q)): ", log(exp(q))); immutable s = q.exp.log; writeln("9.5 let s = log(exp(q)): ", s); writeln(" exp(s): ", exp(s)); writeln(" log(s): ", log(s)); writeln(" exp(log(s)): ", exp(log(s))); writeln(" log(exp(s)): ", log(exp(s))); }  Output: 1. q - norm: 7.34847 2. q - negative: [-2, -3, -4, -5] 3. q - conjugate: [2, -3, -4, -5] 4. r + q: [9, 3, 4, 5] q + r: [9, 3, 4, 5] 5. q1 + q2: [5, 7, 9, 11] 6. r * q: [14, 21, 28, 35] q * r: [14, 21, 28, 35] 7. q1 * q2: [-56, 16, 24, 26] q2 * q1: [-56, 18, 20, 28] 8. q1 * q2 != q2 * Q1 ? true 9.1 i * i: [-1, 0, 0, 0] J * j: [-1, 0, 0, 0] k * k: [-1, 0, 0, 0] i * j * k: [-1, 0, 0, 0] 9.2 q1 / q2: [0.790698, 0.0232558, -1.35525e-20, 0.0465116] 9.3 q1 / q2 * q2: [2, 3, 4, 5] q2 * q1 / q2: [2, 3.46512, 3.90698, 4.76744] 9.4 exp(pi * i): [-1, -5.42101e-20, -0, -0] exp(pi * j): [-1, -0, -5.42101e-20, -0] exp(pi * k): [-1, -0, -0, -5.42101e-20] exp(q): [5.21186, 2.22222, 2.96296, 3.7037] log(q): [1.99449, 0.549487, 0.732649, 0.915812] exp(log(q)): [2, 3, 4, 5] log(exp(q)): [2, 0.33427, 0.445694, 0.557117] 9.5 let s = log(exp(q)): [2, 0.33427, 0.445694, 0.557117] exp(s): [5.21186, 2.22222, 2.96296, 3.7037] log(s): [0.765279, 0.159215, 0.212286, 0.265358] exp(log(s)): [2, 0.33427, 0.445694, 0.557117] log(exp(s)): [2, 0.33427, 0.445694, 0.557117] ## Dart Translation of: Kotlin import 'dart:math' as math; class Quaternion { final double a, b, c, d; Quaternion(this.a, this.b, this.c, this.d); Quaternion operator +(Object other) { if (other is Quaternion) { return Quaternion(a + other.a, b + other.b, c + other.c, d + other.d); } else if (other is double) { return Quaternion(a + other, b, c, d); } throw ArgumentError('Invalid type for addition:${other.runtimeType}');
}

Quaternion operator *(Object other) {
if (other is Quaternion) {
return Quaternion(
a * other.a - b * other.b - c * other.c - d * other.d,
a * other.b + b * other.a + c * other.d - d * other.c,
a * other.c - b * other.d + c * other.a + d * other.b,
a * other.d + b * other.c - c * other.b + d * other.a,
);
} else if (other is double) {
return Quaternion(a * other, b * other, c * other, d * other);
}
throw ArgumentError('Invalid type for multiplication: ${other.runtimeType}'); } Quaternion operator -() => Quaternion(-a, -b, -c, -d); Quaternion conj() => Quaternion(a, -b, -c, -d); double norm() => math.sqrt(a * a + b * b + c * c + d * d); @override String toString() => '($a, $b,$c, $d)'; } void main() { var q = Quaternion(1.0, 2.0, 3.0, 4.0); var q1 = Quaternion(2.0, 3.0, 4.0, 5.0); var q2 = Quaternion(3.0, 4.0, 5.0, 6.0); var r = 7.0; print("q =$q");
print("q1 = $q1"); print("q2 =$q2");
print("r  = $r\n"); print("norm(q) =${q.norm().toStringAsFixed(6)}");
print("-q      = ${-q}"); print("conj(q) =${q.conj()}\n");
print("r  + q  = ${q + r}"); print("q + r =${q + r}");
print("q1 + q2 = ${q1 + q2}\n"); print("r * q =${q * r}");
print("q  * r  = ${q * r}"); var q3 = q1 * q2; var q4 = q2 * q1; print("q1 * q2 =$q3");
print("q2 * q1 = $q4\n"); print("q1 * q2 != q2 * q1 =${q3 != q4}");
}

Output:
q  = (1.0, 2.0, 3.0, 4.0)
q1 = (2.0, 3.0, 4.0, 5.0)
q2 = (3.0, 4.0, 5.0, 6.0)
r  = 7.0

norm(q) = 5.477226
-q      = (-1.0, -2.0, -3.0, -4.0)
conj(q) = (1.0, -2.0, -3.0, -4.0)

r  + q  = (8.0, 2.0, 3.0, 4.0)
q  + r  = (8.0, 2.0, 3.0, 4.0)
q1 + q2 = (5.0, 7.0, 9.0, 11.0)

r  * q  = (7.0, 14.0, 21.0, 28.0)
q  * r  = (7.0, 14.0, 21.0, 28.0)
q1 * q2 = (-56.0, 16.0, 24.0, 26.0)
q2 * q1 = (-56.0, 18.0, 20.0, 28.0)

q1 * q2 != q2 * q1 = true



## Delphi

unit Quaternions;

interface

type

TQuaternion = record
A, B, C, D: double;

function  Init          (aA, aB, aC, aD : double): TQuaternion;
function  Norm          : double;
function  Conjugate     : TQuaternion;
function  ToString      : string;

class operator Negative (Left : TQuaternion): TQuaternion;
class operator Positive (Left : TQuaternion): TQuaternion;
class operator Add      (Left, Right : TQuaternion): TQuaternion;
class operator Subtract (Left, Right : TQuaternion): TQuaternion;
class operator Multiply (Left, Right : TQuaternion): TQuaternion;
class operator Multiply (Left : TQuaternion; Right : double): TQuaternion; overload;
class operator Multiply (Left : double; Right : TQuaternion): TQuaternion; overload;
end;

implementation

uses
SysUtils;

{ TQuaternion }

function TQuaternion.Init(aA, aB, aC, aD: double): TQuaternion;
begin
A := aA;
B := aB;
C := aC;

result := Self;
end;

function TQuaternion.Norm: double;
begin
result := sqrt(sqr(A) + sqr(B) + sqr(C) + sqr(D));
end;

function TQuaternion.Conjugate: TQuaternion;
begin
result.B := -B;
result.C := -C;
result.D := -D;
end;

class operator TQuaternion.Negative(Left: TQuaternion): TQuaternion;
begin
result.A := -Left.A;
result.B := -Left.B;
result.C := -Left.C;
result.D := -Left.D;
end;

class operator TQuaternion.Positive(Left: TQuaternion): TQuaternion;
begin
result := Left;
end;

class operator TQuaternion.Add(Left, Right: TQuaternion): TQuaternion;
begin
result.A := Left.A + Right.A;
result.B := Left.B + Right.B;
result.C := Left.C + Right.C;
result.D := Left.D + Right.D;
end;

class operator TQuaternion.Add(Left: TQuaternion; Right: double): TQuaternion;
begin
result.A := Left.A + Right;
result.B := Left.B;
result.C := Left.C;
result.D := Left.D;
end;

class operator TQuaternion.Add(Left: double; Right: TQuaternion): TQuaternion;
begin
result.A := Left + Right.A;
result.B := Right.B;
result.C := Right.C;
result.D := Right.D;
end;

class operator TQuaternion.Subtract(Left, Right: TQuaternion): TQuaternion;
begin
result.A := Left.A - Right.A;
result.B := Left.B - Right.B;
result.C := Left.C - Right.C;
result.D := Left.D - Right.D;
end;

class operator TQuaternion.Multiply(Left, Right: TQuaternion): TQuaternion;
begin
result.A := Left.A * Right.A - Left.B * Right.B - Left.C * Right.C - Left.D * Right.D;
result.B := Left.A * Right.B + Left.B * Right.A + Left.C * Right.D - Left.D * Right.C;
result.C := Left.A * Right.C - Left.B * Right.D + Left.C * Right.A + Left.D * Right.B;
result.D := Left.A * Right.D + Left.B * Right.C - Left.C * Right.B + Left.D * Right.A;
end;

class operator TQuaternion.Multiply(Left: double; Right: TQuaternion): TQuaternion;
begin
result.A := Left * Right.A;
result.B := Left * Right.B;
result.C := Left * Right.C;
result.D := Left * Right.D;
end;

class operator TQuaternion.Multiply(Left: TQuaternion; Right: double): TQuaternion;
begin
result.A := Left.A * Right;
result.B := Left.B * Right;
result.C := Left.C * Right;
result.D := Left.D * Right;
end;

function TQuaternion.ToString: string;
begin
result := Format('%f + %fi + %fj + %fk', [A, B, C, D]);
end;

end.


Test program

program QuaternionTest;

{$APPTYPE CONSOLE} uses Quaternions in 'Quaternions.pas'; var r : double; q, q1, q2 : TQuaternion; begin r := 7; q := q .Init(1, 2, 3, 4); q1 := q1.Init(2, 3, 4, 5); q2 := q2.Init(3, 4, 5, 6); writeln('q = ', q.ToString); writeln('q1 = ', q1.ToString); writeln('q2 = ', q2.ToString); writeln('r = ', r); writeln('Norm(q ) = ', q.Norm); writeln('Norm(q1) = ', q1.Norm); writeln('Norm(q2) = ', q2.Norm); writeln('-q = ', (-q).ToString); writeln('Conjugate q = ', q.Conjugate.ToString); writeln('q1 + q2 = ', (q1 + q2).ToString); writeln('q2 + q1 = ', (q2 + q1).ToString); writeln('q * r = ', (q * r).ToString); writeln('r * q = ', (r * q).ToString); writeln('q1 * q2 = ', (q1 * q2).ToString); writeln('q2 * q1 = ', (q2 * q1).ToString); end.  Output: q = 1.00 + 2.00i + 3.00j + 4.00k q1 = 2.00 + 3.00i + 4.00j + 5.00k q2 = 3.00 + 4.00i + 5.00j + 6.00k r = 7.00000000000000E+0000 Norm(q ) = 5.47722557505166E+0000 Norm(q1) = 7.34846922834953E+0000 Norm(q2) = 9.27361849549570E+0000 -q = -1.00 + -2.00i + -3.00j + -4.00k Conjugate q = -1.00 + -2.00i + -3.00j + -4.00k q1 + q2 = 5.00 + 7.00i + 9.00j + 11.00k q2 + q1 = 5.00 + 7.00i + 9.00j + 11.00k q * r = 7.00 + 14.00i + 21.00j + 28.00k r * q = 7.00 + 14.00i + 21.00j + 28.00k q1 * q2 = -56.00 + 16.00i + 24.00j + 26.00k q2 * q1 = -56.00 + 18.00i + 20.00j + 28.00k  --DavidIzadaR 20:33, 7 August 2011 (UTC) ## E interface Quaternion guards QS {} def makeQuaternion(a, b, c, d) { return def quaternion implements QS { to __printOn(out) { out.print("(", a, " + ", b, "i + ") out.print(c, "j + ", d, "k)") } # Task requirement 1 to norm() { return (a**2 + b**2 + c**2 + d**2).sqrt() } # Task requirement 2 to negate() { return makeQuaternion(-a, -b, -c, -d) } # Task requirement 3 to conjugate() { return makeQuaternion(a, -b, -c, -d) } # Task requirement 4, 5 # This implements q + r; r + q is deliberately prohibited by E to add(other :any[Quaternion, int, float64]) { switch (other) { match q :Quaternion { return makeQuaternion( a+q.a(), b+q.b(), c+q.c(), d+q.d()) } match real { return makeQuaternion(a+real, b, c, d) } } } # Task requirement 6, 7 # This implements q * r; r * q is deliberately prohibited by E to multiply(other :any[Quaternion, int, float64]) { switch (other) { match q :Quaternion { return makeQuaternion( a*q.a() - b*q.b() - c*q.c() - d*q.d(), a*q.b() + b*q.a() + c*q.d() - d*q.c(), a*q.c() - b*q.d() + c*q.a() + d*q.b(), a*q.d() + b*q.c() - c*q.b() + d*q.a()) } match real { return makeQuaternion(real*a, real*b, real*c, real*d) } } } to a() { return a } to b() { return b } to c() { return c } to d() { return d } } } ? def q1 := makeQuaternion(2,3,4,5) # value: (2 + 3i + 4j + 5k) ? def q2 := makeQuaternion(3,4,5,6) # value: (3 + 4i + 5j + 6k) ? q1+q2 # value: (5 + 7i + 9j + 11k) ? q1*q2 # value: (-56 + 16i + 24j + 26k) ? q2*q1 # value: (-56 + 18i + 20j + 28k) ? q1+(-2) # value: (0 + 3i + 4j + 5k) ## EasyLang func qnorm q[] . for i to 4 s += q[i] * q[i] . return sqrt s . func[] qneg q[] . for i to 4 q[i] = -q[i] . return q[] . func[] qconj q[] . for i = 2 to 4 q[i] = -q[i] . return q[] . func[] qaddreal q[] r . q[1] += r return q[] . func[] qadd q[] q2[] . for i to 4 q[i] += q2[i] . return q[] . func[] qmulreal q[] r . for i to 4 q[i] *= r . return q[] . func[] qmul q1[] q2[] . res[] &= q1[1] * q2[1] - q1[2] * q2[2] - q1[3] * q2[3] - q1[4] * q2[4] res[] &= q1[1] * q2[2] + q1[2] * q2[1] + q1[3] * q2[4] - q1[4] * q2[3] res[] &= q1[1] * q2[3] - q1[2] * q2[4] + q1[3] * q2[1] + q1[4] * q2[2] res[] &= q1[1] * q2[4] + q1[2] * q2[3] - q1[3] * q2[2] + q1[4] * q2[1] return res[] . q[] = [ 1 2 3 4 ] q1[] = [ 2 3 4 5 ] q2[] = [ 3 4 5 6 ] r = 7 # print "q = " & q[] print "q1 = " & q1[] print "q2 = " & q2[] print "r = " & r print "norm(q) = " & qnorm q[] print "neg(q) = " & qneg q[] print "conjugate(q) = " & qconj q[] print "q+r = " & qaddreal q[] r print "q1+q2 = " & qadd q1[] q2[] print "qr = " & qmulreal q[] r print "q1q2 = " & qmul q1[] q2[] print "q2q1 = " & qmul q2[] q1[] if q1[] <> q2[] print "q1 != q2" .  Output: q = [ 1 2 3 4 ] q1 = [ 2 3 4 5 ] q2 = [ 3 4 5 6 ] r = 7 norm(q) = 5.48 neg(q) = [ -1 -2 -3 -4 ] conjugate(q) = [ 1 -2 -3 -4 ] q+r = [ 8 2 3 4 ] q1+q2 = [ 5 7 9 11 ] qr = [ 7 14 21 28 ] q1q2 = [ -56 16 24 26 ] q2q1 = [ -56 18 20 28 ] q1 != q2  ## Eero #import <Foundation/Foundation.h> interface Quaternion : Number // Properties -- note that this is an immutable class. double real, i, j, k {readonly} end implementation Quaternion initWithReal: double, i: double, j: double, k: double, return instancetype self = super.init if self _real = real; _i = i; _j = j; _k = k return self +new: double real, ..., return instancetype va_list args va_start(args, real) object := Quaternion.alloc.initWithReal: real, i: va_arg(args, double), j: va_arg(args, double), k: va_arg(args, double) va_end(args) return object descriptionWithLocale: id, return String = String.stringWithFormat: '(%.1f, %.1f, %.1f, %.1f)', self.real, self.i, self.j, self.k norm, return double = sqrt(self.real * self.real + self.i * self.i + self.j * self.j + self.k * self.k) negative, return Quaternion = Quaternion.new: -self.real, -self.i, -self.j, -self.k conjugate, return Quaternion = Quaternion.new: self.real, -self.i, -self.j, -self.k // Overload "+" operator (left operand is Quaternion) plus: Number operand, return Quaternion real := self.real, i = self.i, j = self.j, k = self.k if operand.isKindOfClass: Quaternion.class q := (Quaternion)operand real += q.real; i += q.i; j += q.j; k += q.k else real += (double)operand return Quaternion.new: real, i, j, k // Overload "*" operator (left operand is Quaternion) multipliedBy: Number operand, return Quaternion real := self.real, i = self.i, j = self.j, k = self.k if operand.isKindOfClass: Quaternion.class q := (Quaternion)operand real = self.real * q.real - self.i* q.i - self.j * q.j - self.k * q.k i = self.real * q.i + self.i * q.real + self.j * q.k - self.k * q.j j = self.real * q.j - self.i * q.k + self.j * q.real + self.k * q.i k = self.real * q.k + self.i * q.j - self.j * q.i + self.k * q.real else real *= (double)operand i *= (double)operand; j *= (double)operand; k *= (double)operand return Quaternion.new: real, i, j, k end implementation Number (QuaternionOperators) // Overload "+" operator (left operand is Number) plus: Quaternion operand, return Quaternion real := (double)self + operand.real return Quaternion.new: real, operand.i, operand.j, operand.k // Overload "*" operator (left operand is Number) multipliedBy: Quaternion operand, return Quaternion r := (double)self return Quaternion.new: r * operand.real, r * operand.i, r * operand.j, r * operand.k end int main() autoreleasepool q := Quaternion.new: 1.0, 2.0, 3.0, 4.0 q1 := Quaternion.new: 2.0, 3.0, 4.0, 5.0 q2 := Quaternion.new: 3.0, 4.0, 5.0, 6.0 Log( 'q = %@', q ) Log( 'q1 = %@', q1 ) Log( 'q2 = %@\n\n', q2 ) Log( 'q norm = %.3f', q.norm ) Log( 'q negative = %@', q.negative ) Log( 'q conjugate = %@', q.conjugate ) Log( '7 + q = %@', 7.0 + q ) Log( 'q + 7 = %@', q + 7.0 ) Log( 'q1 + q2 = %@', q1 + q2 ) Log( '7 * q = %@', 7 * q) Log( 'q * 7 = %@', q * 7.0 ) Log( 'q1 * q2 = %@', q1 * q2 ) Log( 'q2 * q1 = %@', q2 * q1 ) return 0  Output: 2013-09-04 16:40:29.818 a.out[2170:507] q = (1.0, 2.0, 3.0, 4.0) 2013-09-04 16:40:29.819 a.out[2170:507] q1 = (2.0, 3.0, 4.0, 5.0) 2013-09-04 16:40:29.820 a.out[2170:507] q2 = (3.0, 4.0, 5.0, 6.0) 2013-09-04 16:40:29.820 a.out[2170:507] q norm = 5.477 2013-09-04 16:40:29.820 a.out[2170:507] q negative = (-1.0, -2.0, -3.0, -4.0) 2013-09-04 16:40:29.820 a.out[2170:507] q conjugate = (1.0, -2.0, -3.0, -4.0) 2013-09-04 16:40:29.821 a.out[2170:507] 7 + q = (8.0, 2.0, 3.0, 4.0) 2013-09-04 16:40:29.821 a.out[2170:507] q + 7 = (8.0, 2.0, 3.0, 4.0) 2013-09-04 16:40:29.821 a.out[2170:507] q1 + q2 = (5.0, 7.0, 9.0, 11.0) 2013-09-04 16:40:29.821 a.out[2170:507] 7 * q = (7.0, 14.0, 21.0, 28.0) 2013-09-04 16:40:29.821 a.out[2170:507] q * 7 = (7.0, 14.0, 21.0, 28.0) 2013-09-04 16:40:29.822 a.out[2170:507] q1 * q2 = (-56.0, 16.0, 24.0, 26.0) 2013-09-04 16:40:29.822 a.out[2170:507] q2 * q1 = (-56.0, 18.0, 20.0, 28.0) ## Elena Translation of: C# ELENA 6.x : import system'math; import extensions; import extensions'text; struct Quaternion { real A : rprop; real B : rprop; real C : rprop; real D : rprop; constructor new(a, b, c, d) <= new(cast real(a), cast real(b), cast real(c), cast real(d)); constructor new(real a, real b, real c, real d) { A := a; B := b; C := c; D := d } constructor(real r) { A := r; B := 0.0r; C := 0.0r; D := 0.0r } real Norm = (A*A + B*B + C*C + D*D).sqrt(); Quaternion Negative = Quaternion.new(A.Negative,B.Negative,C.Negative,D.Negative); Quaternion Conjugate = Quaternion.new(A,B.Negative,C.Negative,D.Negative); Quaternion add(Quaternion q) = Quaternion.new(A + q.A, B + q.B, C + q.C, D + q.D); Quaternion multiply(Quaternion q) = Quaternion.new( A * q.A - B * q.B - C * q.C - D * q.D, A * q.B + B * q.A + C * q.D - D * q.C, A * q.C - B * q.D + C * q.A + D * q.B, A * q.D + B * q.C - C * q.B + D * q.A); Quaternion add(real r) <= add(Quaternion.new(r,0,0,0)); Quaternion multiply(real r) <= multiply(Quaternion.new(r,0,0,0)); bool equal(Quaternion q) = (A == q.A) && (B == q.B) && (C == q.C) && (D == q.D); string toPrintable() = new StringWriter().printFormatted("Q({0}, {1}, {2}, {3})",A,B,C,D); } public program() { auto q := Quaternion.new(1,2,3,4); auto q1 := Quaternion.new(2,3,4,5); auto q2 := Quaternion.new(3,4,5,6); real r := 7; console.printLine("q = ", q); console.printLine("q1 = ", q1); console.printLine("q2 = ", q2); console.printLine("r = ", r); console.printLine("q.Norm() = ", q.Norm); console.printLine("q1.Norm() = ", q1.Norm); console.printLine("q2.Norm() = ", q2.Norm); console.printLine("-q = ", q.Negative); console.printLine("q.Conjugate() = ", q.Conjugate); console.printLine("q + r = ", q + r); console.printLine("q1 + q2 = ", q1 + q2); console.printLine("q2 + q1 = ", q2 + q1); console.printLine("q * r = ", q * r); console.printLine("q1 * q2 = ", q1 * q2); console.printLine("q2 * q1 = ", q2 * q1); console.printLineFormatted("q1*q2 {0} q2*q1", ((q1 * q2) == (q2 * q1)).iif("==","!=")) } Output: q = Q(1.0, 2.0, 3.0, 4.0) q1 = Q(2.0, 3.0, 4.0, 5.0) q2 = Q(3.0, 4.0, 5.0, 6.0) r = 7.0 q.Norm() = 5.477225575052 q1.Norm() = 7.34846922835 q2.Norm() = 9.273618495496 -q = Q(-1.0, -2.0, -3.0, -4.0) q.Conjugate() = Q(1.0, -2.0, -3.0, -4.0) q + r = Q(8.0, 2.0, 3.0, 4.0) q1 + q2 = Q(5.0, 7.0, 9.0, 11.0) q2 + q1 = Q(5.0, 7.0, 9.0, 11.0) q * r = Q(7.0, 14.0, 21.0, 28.0) q1 * q2 = Q(-56.0, 16.0, 24.0, 26.0) q2 * q1 = Q(-56.0, 18.0, 20.0, 28.0) q1*q2 != q2*q1  ## ERRE PROGRAM QUATERNION !$DOUBLE

TYPE QUATERNION=(A,B,C,D)

DIM Q:QUATERNION,Q1:QUATERNION,Q2:QUATERNION

DIM R:QUATERNION,S:QUATERNION,T:QUATERNION

PROCEDURE NORM(T.->NORM)
NORM=SQR(T.A*T.A+T.B*T.B+T.C*T.C+T.D*T.D)
END PROCEDURE

PROCEDURE NEGATIVE(T.->T.)
T.A=-T.A
T.B=-T.B
T.C=-T.C
T.D=-T.D
END PROCEDURE

PROCEDURE CONJUGATE(T.->T.)
T.A=T.A
T.B=-T.B
T.C=-T.C
T.D=-T.D
END PROCEDURE

T.A=T.A+REAL
T.B=T.B
T.C=T.C
T.D=T.D
END PROCEDURE

T.A=T.A+S.A
T.B=T.B+S.B
T.C=T.C+S.C
T.D=T.D+S.D
END PROCEDURE

PROCEDURE MULT_REAL(T.,REAL->T.)
T.A=T.A*REAL
T.B=T.B*REAL
T.C=T.C*REAL
T.D=T.D*REAL
END PROCEDURE

PROCEDURE MULT(T.,S.->R.)
R.A=T.A*S.A-T.B*S.B-T.C*S.C-T.D*S.D
R.B=T.A*S.B+T.B*S.A+T.C*S.D-T.D*S.C
R.C=T.A*S.C-T.B*S.D+T.C*S.A+T.D*S.B
R.D=T.A*S.D+T.B*S.C-T.C*S.B+T.D*S.A
END PROCEDURE

PROCEDURE PRINTQ(T.)
PRINT("(";T.A;",";T.B;",";T.C;",";T.D;")")
END PROCEDURE

BEGIN
Q.A=1  Q.B=2  Q.C=3  Q.D=4
Q1.A=2 Q1.B=3 Q1.C=4 Q1.D=5
Q2.A=3 Q2.B=4 Q2.C=5 Q2.D=6
REAL=7

NORM(Q.->NORM)
PRINT("Norm(q)=";NORM)

NEGATIVE(Q.->T.)
PRINT("Negative(q) =";)
PRINTQ(T.)

CONJUGATE(Q.->T.)
PRINT("Conjugate(q) =";)
PRINTQ(T.)

PRINT("q + real =";)
PRINTQ(T.)

PRINT("q1 + q2 =";)
PRINTQ(T.)

PRINT("q2 + q1 = ";)
PRINTQ(T.)

MULT_REAL(Q.,REAL->T.)
PRINT("q * real =";)
PRINTQ(T.)

! multiplication is not commutative
MULT(Q1.,Q2.->R.)
PRINT("q1 * q2=";)
PRINTQ(R.)

MULT(Q2.,Q1.->R.)
PRINT("q2 * q1=";)
PRINTQ(R.)
END PROGRAM

## Euphoria

function norm(sequence q)
return sqrt(power(q[1],2)+power(q[2],2)+power(q[3],2)+power(q[4],2))
end function

function conj(sequence q)
q[2..4] = -q[2..4]
return q
end function

if atom(q1) != atom(q2) then
if atom(q1) then
q1 = {q1,0,0,0}
else
q2 = {q2,0,0,0}
end if
end if
return q1+q2
end function

function mul(object q1, object q2)
if sequence(q1) and sequence(q2) then
return { q1[1]*q2[1] - q1[2]*q2[2] - q1[3]*q2[3] - q1[4]*q2[4],
q1[1]*q2[2] + q1[2]*q2[1] + q1[3]*q2[4] - q1[4]*q2[3],
q1[1]*q2[3] - q1[2]*q2[4] + q1[3]*q2[1] + q1[4]*q2[2],
q1[1]*q2[4] + q1[2]*q2[3] - q1[3]*q2[2] + q1[4]*q2[1] }
else
return q1*q2
end if
end function

function quats(sequence q)
return sprintf("%g + %gi + %gj + %gk",q)
end function

constant
q  = {1, 2, 3, 4},
q1 = {2, 3, 4, 5},
q2 = {5, 6, 7, 8},
r  = 7

printf(1, "norm(q) = %g\n", norm(q))
printf(1, "-q = %s\n", {quats(-q)})
printf(1, "conj(q) = %s\n", {quats(conj(q))})
printf(1, "q + r = %s\n", {quats(add(q,r))})
printf(1, "q1 + q2 = %s\n", {quats(add(q1,q2))})
printf(1, "q1 * q2 = %s\n", {quats(mul(q1,q2))})
printf(1, "q2 * q1 = %s\n", {quats(mul(q2,q1))})
Output:
norm(q) = 5.47723
-q = -1 + -2i + -3j + -4k
conj(q) = 1 + -2i + -3j + -4k
q + r = 8 + 2i + 3j + 4k
q1 + q2 = 7 + 9i + 11j + 13k
q1 * q2 = -76 + 24i + 40j + 38k
q2 * q1 = -76 + 30i + 28j + 44k

## F#

Mainly a

Translation of: C#

On the minus side we have no way to define a conversion to Quaternion from any suitable (numeric) type.

On the plus side we can avoid the stuff to make the equality structual (from the referential equality default) by just declaring it as an attribute to the type and let the compiler handle the details.

open System

[<Struct; StructuralEquality; NoComparison>]
type Quaternion(r : float, i : float, j : float, k : float) =
member this.A = r
member this.B = i
member this.C = j
member this.D = k

new (f : float) = Quaternion(f, 0., 0., 0.)

static member (~-) (q : Quaternion) = Quaternion(-q.A, -q.B, -q.C, -q.D)

static member (+) (q1 : Quaternion, q2 : Quaternion) =
Quaternion(q1.A + q2.A, q1.B + q2.B, q1.C + q2.C, q1.D + q2.D)
static member (+) (q : Quaternion, r : float) = q + Quaternion(r)
static member (+) (r : float, q: Quaternion) = Quaternion(r) + q

static member (*) (q1 : Quaternion, q2 : Quaternion) =
Quaternion(
q1.A * q2.A - q1.B * q2.B - q1.C * q2.C - q1.D * q2.D,
q1.A * q2.B + q1.B * q2.A + q1.C * q2.D - q1.D * q2.C,
q1.A * q2.C - q1.B * q2.D + q1.C * q2.A + q1.D * q2.B,
q1.A * q2.D + q1.B * q2.C - q1.C * q2.B + q1.D * q2.A)
static member (*) (q : Quaternion, r : float) = q * Quaternion(r)
static member (*) (r : float, q: Quaternion) = Quaternion(r) * q

member this.Norm = Math.Sqrt(r * r + i * i + j * j + k * k)

member this.Conjugate = Quaternion(r, -i, -j, -k)

override this.ToString() = sprintf "Q(%f, %f, %f, %f)" r i j k

[<EntryPoint>]
let main argv =
let q = Quaternion(1., 2., 3., 4.)
let q1 = Quaternion(2., 3., 4., 5.)
let q2 = Quaternion(3., 4., 5., 6.)
let r = 7.

printfn "q = %A" q
printfn "q1 = %A" q1
printfn "q2 = %A" q2
printfn "r = %A" r

printfn "q.Norm = %A" q.Norm
printfn "q1.Norm = %A" q1.Norm
printfn "q2.Norm = %A" q2.Norm

printfn "-q = %A" -q
printfn "q.Conjugate = %A" q.Conjugate

printfn "q + r = %A" (q + (Quaternion r))
printfn "q1 + q2 = %A" (q1 + q2)
printfn "q2 + q1 = %A" (q2 + q1)

printfn "q * r = %A" (q * r)
printfn "q1 * q2 = %A" (q1 * q2)
printfn "q2 * q1 = %A" (q2 * q1)

printfn "q1*q2 %s q2*q1" (if (q1 * q2) = (q2 * q1) then "=" else "<>")
printfn "q %s Q(1.,2.,3.,4.)" (if q = Quaternion(1., 2., 3., 4.) then "=" else "<>")
0

Output:
q = Q(1.000000, 2.000000, 3.000000, 4.000000)
q1 = Q(2.000000, 3.000000, 4.000000, 5.000000)
q2 = Q(3.000000, 4.000000, 5.000000, 6.000000)
r = 7.0
q.Norm = 5.477225575
q1.Norm = 7.348469228
q2.Norm = 9.273618495
-q = Q(-1.000000, -2.000000, -3.000000, -4.000000)
q.Conjugate = Q(1.000000, -2.000000, -3.000000, -4.000000)
q + r = Q(8.000000, 2.000000, 3.000000, 4.000000)
q1 + q2 = Q(5.000000, 7.000000, 9.000000, 11.000000)
q2 + q1 = Q(5.000000, 7.000000, 9.000000, 11.000000)
q * r = Q(7.000000, 14.000000, 21.000000, 28.000000)
q1 * q2 = Q(-56.000000, 16.000000, 24.000000, 26.000000)
q2 * q1 = Q(-56.000000, 18.000000, 20.000000, 28.000000)
q1*q2 <> q2*q1
q = Q(1.,2.,3.,4.)

## Factor

The math.quaternions vocabulary provides words for treating sequences like quaternions. norm and vneg come from the math.vectors vocabulary. Oddly, I wasn't able to find a word for adding a real to a quaternion, so I wrote one.

USING: generalizations io kernel locals math.quaternions
math.vectors prettyprint sequences ;
IN: rosetta-code.quaternion-type

: show ( quot -- )
[ unparse 2 tail but-last "= " append write ] [ call . ] bi
; inline

: 2show ( quots -- )
[ 2curry show ] map-compose [ call ] each ; inline

: q+n ( q n -- q+n ) n>q q+ ;

[let
{ 1 2 3 4 } 7 { 2 3 4 5 } { 3 4 5 6 } :> ( q r q1 q2 )
q [ norm ]
q [ vneg ]
q [ qconjugate ]
[ curry show ] 2tri@
{
[ q  r  [ q+n ] ]
[ q  r  [ q*n ] ]
[ q1 q2 [ q+  ] ]
[ q1 q2 [ q*  ] ]
[ q2 q1 [ q*  ] ]
} 2show
]

Output:
{ 1 2 3 4 } norm = 5.477225575051661
{ 1 2 3 4 } vneg = { -1 -2 -3 -4 }
{ 1 2 3 4 } qconjugate = { 1 -2 -3 -4 }
{ 1 2 3 4 } 7 q+n = { 8 2 3 4 }
{ 1 2 3 4 } 7 q*n = { 7 14 21 28 }
{ 2 3 4 5 } { 3 4 5 6 } q+ = { 5 7 9 11 }
{ 2 3 4 5 } { 3 4 5 6 } q* = { -56 16 24 26 }
{ 3 4 5 6 } { 2 3 4 5 } q* = { -56 18 20 28 }


## Forth

: quaternions  4 * floats ;

: qvariable create 1 quaternions allot ;

: q! ( a b c d q -- )
dup 3 floats + f!  dup 2 floats + f!  dup float+ f!  f! ;

: qcopy ( src dest -- ) 1 quaternions move ;

: qnorm  ( q -- f )
0e 4 0 do  dup f@ fdup f* f+  float+ loop drop fsqrt ;

: qf* ( q f -- )
4 0 do dup f@ fover f* dup f!  float+ loop fdrop drop ;

: qnegate ( q -- )  -1e qf* ;

: qconj ( q -- )
float+ 3 0 do dup f@ fnegate dup f!  float+ loop drop ;

: qf+ ( q f -- ) dup f@ f+ f! ;

: q+ ( q1 q2 -- )
4 0 do over f@ dup f@ f+ dup f!  float+ swap float+ swap loop 2drop ;

\ access
: q.a             f@ ;
: q.b      float+ f@ ;
: q.c  2 floats + f@ ;
: q.d  3 floats + f@ ;

: q* ( dest q1 q2 -- )
over q.a dup q.d f*  over q.b dup q.c f* f+  over q.c dup q.b f* f-  over q.d dup q.a f* f+
over q.a dup q.c f*  over q.b dup q.d f* f-  over q.c dup q.a f* f+  over q.d dup q.b f* f+
over q.a dup q.b f*  over q.b dup q.a f* f+  over q.c dup q.d f* f+  over q.d dup q.c f* f-
over q.a dup q.a f*  over q.b dup q.b f* f-  over q.c dup q.c f* f-  over q.d dup q.d f* f-
2drop  4 0 do dup f!  float+ loop  drop ;

: q= ( q1 q2 -- ? )
4 0 do
over f@ dup f@ f<> if 2drop false unloop exit then
float+ swap float+
loop
2drop true ;

\ testing

: q. ( q -- )
[char] ( emit space
4 0 do dup f@ f.  float+ loop drop
[char] ) emit space ;

qvariable q   1e 2e 3e 4e q  q!
qvariable q1  2e 3e 4e 5e q1 q!
create q2     3e f, 4e f, 5e f, 6e f,	\ by hand

qvariable tmp
qvariable m1
qvariable m2

q qnorm f.				\ 5.47722557505166
q tmp qcopy  tmp qnegate  tmp q.	\ ( -1. -2. -3. -4. )
q tmp qcopy  tmp qconj    tmp q.	\ ( 1. -2. -3. -4. )

q m1 qcopy  m1 7e qf+   m1 q.		\ ( 8. 2. 3. 4. )
q m2 qcopy  7e m2 qf+   m2 q.		\ ( 8. 2. 3. 4. )
m1 m2 q= .				\ -1  (true)

q2 tmp qcopy  q1 tmp q+   tmp q.	\ ( 5. 7. 9. 11. )

q m1 qcopy  m1 7e qf*     m1 q.		\ ( 7. 14. 21. 28. )
q m2 qcopy  7e m2 qf*     m2 q.		\ ( 7. 14. 21. 28. )
m1 m2 q= .				\ -1  (true)

m1 q1 q2 q*  m1 q.			\ ( -56. 16. 24. 26. )
m2 q2 q1 q*  m2 q.			\ ( -56. 18. 20. 28. )
m1 m2 q= .				\ 0  (false)


## Fortran

Works with: Fortran version 90 and later
module Q_mod
implicit none

type quaternion
real :: a, b, c, d
end type

public :: norm, neg, conj
public :: operator (+)
public :: operator (*)

private ::  q_plus_q, q_plus_r, r_plus_q, &
q_mult_q, q_mult_r, r_mult_q, &
norm_q, neg_q, conj_q

interface norm
module procedure norm_q
end interface

interface neg
module procedure neg_q
end interface

interface conj
module procedure conj_q
end interface

interface operator (+)
module procedure q_plus_q, q_plus_r, r_plus_q
end interface

interface operator (*)
module procedure q_mult_q, q_mult_r, r_mult_q
end interface

contains

function norm_q(x) result(res)
real :: res
type (quaternion), intent (in) :: x

res = sqrt(x%a*x%a + x%b*x%b + x%c*x%c + x%d*x%d)

end function norm_q

function neg_q(x) result(res)
type (quaternion) :: res
type (quaternion), intent (in) :: x

res%a = -x%a
res%b = -x%b
res%c = -x%c
res%d = -x%d

end function neg_q

function conj_q(x) result(res)
type (quaternion) :: res
type (quaternion), intent (in) :: x

res%a = x%a
res%b = -x%b
res%c = -x%c
res%d = -x%d

end function conj_q

function q_plus_q(x, y) result (res)
type (quaternion) :: res
type (quaternion), intent (in) :: x, y

res%a = x%a + y%a
res%b = x%b + y%b
res%c = x%c + y%c
res%d = x%d + y%d

end function q_plus_q

function q_plus_r(x, r) result (res)
type (quaternion) :: res
type (quaternion), intent (in) :: x
real, intent(in) :: r

res = x
res%a = x%a + r

end function q_plus_r

function r_plus_q(r, x) result (res)
type (quaternion) :: res
type (quaternion), intent (in) :: x
real, intent(in) :: r

res = x
res%a = x%a + r

end function r_plus_q

function q_mult_q(x, y) result (res)
type (quaternion) :: res
type (quaternion), intent (in) :: x, y

res%a = x%a*y%a - x%b*y%b - x%c*y%c - x%d*y%d
res%b = x%a*y%b + x%b*y%a + x%c*y%d - x%d*y%c
res%c = x%a*y%c - x%b*y%d + x%c*y%a + x%d*y%b
res%d = x%a*y%d + x%b*y%c - x%c*y%b + x%d*y%a

end function q_mult_q

function q_mult_r(x, r) result (res)
type (quaternion) :: res
type (quaternion), intent (in) :: x
real, intent(in) ::  r

res%a = x%a*r
res%b = x%b*r
res%c = x%c*r
res%d = x%d*r

end function q_mult_r

function r_mult_q(r, x) result (res)
type (quaternion) :: res
type (quaternion), intent (in) :: x
real, intent(in) ::  r

res%a = x%a*r
res%b = x%b*r
res%c = x%c*r
res%d = x%d*r

end function r_mult_q
end module Q_mod

program Quaternions
use Q_mod
implicit none

real :: r = 7.0
type(quaternion) :: q, q1, q2

q  = quaternion(1, 2, 3, 4)
q1 = quaternion(2, 3, 4, 5)
q2 = quaternion(3, 4, 5, 6)

write(*, "(a, 4f8.3)") "             q = ", q
write(*, "(a, 4f8.3)") "            q1 = ", q1
write(*, "(a, 4f8.3)") "            q2 = ", q2
write(*, "(a, f8.3)")  "             r = ", r
write(*, "(a, f8.3)")  "     Norm of q = ", norm(q)
write(*, "(a, 4f8.3)") " Negative of q = ", neg(q)
write(*, "(a, 4f8.3)") "Conjugate of q = ", conj(q)
write(*, "(a, 4f8.3)") "         q + r = ", q + r
write(*, "(a, 4f8.3)") "         r + q = ", r + q
write(*, "(a, 4f8.3)") "       q1 + q2 = ", q1 + q2
write(*, "(a, 4f8.3)") "         q * r = ", q * r
write(*, "(a, 4f8.3)") "         r * q = ", r * q
write(*, "(a, 4f8.3)") "       q1 * q2 = ", q1 * q2
write(*, "(a, 4f8.3)") "       q2 * q1 = ", q2 * q1

end program

Output:
             q =    1.000   2.000   3.000   4.000
q1 =    2.000   3.000   4.000   5.000
q2 =    3.000   4.000   5.000   6.000
r =    7.000
Norm of q =    5.477
Negative of q =   -1.000  -2.000  -3.000  -4.000
Conjugate of q =    1.000  -2.000  -3.000  -4.000
q + r =    8.000   2.000   3.000   4.000
r + q =    8.000   2.000   3.000   4.000
q1 + q2 =    5.000   7.000   9.000  11.000
q * r =    7.000  14.000  21.000  28.000
r * q =    7.000  14.000  21.000  28.000
q1 * q2 =  -56.000  16.000  24.000  26.000
q2 * q1 =  -56.000  18.000  20.000  28.000

## FreeBASIC

Dim Shared As Integer q(3)  = {1, 2, 3, 4}
Dim Shared As Integer q1(3) = {2, 3, 4, 5}
Dim Shared As Integer q2(3) = {3, 4, 5, 6}
Dim Shared As Integer i, r = 7, t(3)

Function q_norm(q() As Integer) As Double
' medida o valor absoluto de un cuaternión
Dim As Double a = 0
For i = 0 To 3
a += q(i)^2
Next i
Return Sqr(a)
End Function

Sub q_neg(q() As Integer)
For i = 0 To 3
q(i) *= -1
Next i
End Sub

Sub q_conj(q() As Integer)
For i = 1 To 3
q(i) *= -1
Next i
End Sub

Sub q_addreal(q() As Integer, r As Integer)
q(0) += r
End Sub

Sub q_add(q() As Integer, r() As Integer)
For i = 0 To 3
q(i) += r(i)
Next i
End Sub

Sub q_mulreal(q() As Integer, r As Integer)
For i = 0 To 3
q(i) *= r
Next i
End Sub

Sub q_mul(q() As Integer, r() As Integer)
' producto entre cuaternios
Dim As Integer m(3)
m(0) = q(0)*r(0) - q(1)*r(1) - q(2)*r(2) - q(3)*r(3)
m(1) = q(0)*r(1) + q(1)*r(0) + q(2)*r(3) - q(3)*r(2)
m(2) = q(0)*r(2) - q(1)*r(3) + q(2)*r(0) + q(3)*r(1)
m(3) = q(0)*r(3) + q(1)*r(2) - q(2)*r(1) + q(3)*r(0)
For i = 0 To 3 : q(i) = m(i) : Next i
End Sub

Function q_show(q() As Integer) As String
Dim As String a = "("
For i = 0 To 3
a += Str(q(i)) + ", "
Next i
Return Mid(a,1,Len(a)-2) + ")"
End Function

'--- Programa Principal ---
Print " q = "; q_show(q())
Print "q1 = "; q_show(q1())
Print "q2 = "; q_show(q2())
Print " r = "; r
Print "norm(q) ="; q_norm(q())
For i = 0 To 3 : t(i) = q(i) : Next i : q_neg(t())  : Print " neg(q) = "; q_show(t())
For i = 0 To 3 : t(i) = q(i) : Next i : q_conj(t()) : Print "conj(q) = "; q_show(t())
For i = 0 To 3 : t(i) = q(i) : Next i : q_addreal(t(),r) : Print " r + q  = "; q_show(t())
For i = 0 To 3 : t(i) = q1(i) : Next i : q_add(t(),q2()) : Print "q1 + q2 = "; q_show(t())
For i = 0 To 3 : t(i) = q2(i) : Next i : q_add(t(),q1()) : Print "q2 + q1 = "; q_show(t())
For i = 0 To 3 : t(i) = q(i) : Next i : q_mulreal(t(),r) : Print " r * q  = "; q_show(t())
For i = 0 To 3 : t(i) = q1(i) : Next i : q_mul(t(),q2()) : Print "q1 * q2 = "; q_show(t())
For i = 0 To 3 : t(i) = q2(i) : Next i : q_mul(t(),q1()) : Print "q2 * q1 = "; q_show(t())
End

Output:
 q = (1, 2, 3, 4)
q1 = (2, 3, 4, 5)
q2 = (3, 4, 5, 6)
r = 7
norm(q) = 5.477225575051661
neg(q)  = (-1, -2, -3, -4)
conj(q) = (1, -2, -3, -4)
r + q  = (8, 2, 3, 4)
q1 + q2 = (5, 7, 9, 11)
q2 + q1 = (5, 7, 9, 11)
r * q  = (7, 14, 21, 28)
q1 * q2 = (-56, 16, 24, 26)
q2 * q1 = (-56, 18, 20, 28)


## GAP

# GAP has built-in support for quaternions

A := QuaternionAlgebra(Rationals);
# <algebra-with-one of dimension 4 over Rationals>

b := BasisVectors(Basis(A));
# [ e, i, j, k ]

q := [1, 2, 3, 4]*b;
# e+(2)*i+(3)*j+(4)*k

# Conjugate
ComplexConjugate(q);
# e+(-2)*i+(-3)*j+(-4)*k

# Division
1/q;
# (1/30)*e+(-1/15)*i+(-1/10)*j+(-2/15)*k

# Computing norm may be difficult, since the result would be in a quadratic field.
# Sqrt exists in GAP, but it is quite unusual: see ?E in GAP documentation, and the following example
Sqrt(5/3);
# 1/3*E(60)^7+1/3*E(60)^11-1/3*E(60)^19-1/3*E(60)^23-1/3*E(60)^31+1/3*E(60)^43-1/3*E(60)^47+1/3*E(60)^59

# However, the square of the norm is easy to compute
q*ComplexConjugate(q);
# (30)*e

q1 := [2, 3, 4, 5]*b;
# (2)*e+(3)*i+(4)*j+(5)*k

q2 := [3, 4, 5, 6]*b;
# (3)*e+(4)*i+(5)*j+(6)*k

q1*q2 - q2*q1;
# (-2)*i+(4)*j+(-2)*k

# Can't add directly to a rational, one must make a quaternion of it
r := 5/3*b[1];
# (5/3)*e
r + q;
# (8/3)*e+(2)*i+(3)*j+(4)*k

# For multiplication, no problem (we are in an algebra over rationals !)
r*q;
# (5/3)*e+(10/3)*i+(5)*j+(20/3)*k
5/3*q;
# (5/3)*e+(10/3)*i+(5)*j+(20/3)*k

# Negative
-q;
(-1)*e+(-2)*i+(-3)*j+(-4)*k

# While quaternions are built-in, you can define an algebra in GAP by specifying it's multiplication table.
# See tutorial, p. 60, and reference of the functions used below.

# A multiplication table of dimension 4.

T := EmptySCTable(4, 0);
SetEntrySCTable(T, 1, 1, [1, 1]);
SetEntrySCTable(T, 1, 2, [1, 2]);
SetEntrySCTable(T, 1, 3, [1, 3]);
SetEntrySCTable(T, 1, 4, [1, 4]);
SetEntrySCTable(T, 2, 1, [1, 2]);
SetEntrySCTable(T, 2, 2, [-1, 1]);
SetEntrySCTable(T, 2, 3, [1, 4]);
SetEntrySCTable(T, 2, 4, [-1, 3]);
SetEntrySCTable(T, 3, 1, [1, 3]);
SetEntrySCTable(T, 3, 2, [-1, 4]);
SetEntrySCTable(T, 3, 3, [-1, 1]);
SetEntrySCTable(T, 3, 4, [1, 2]);
SetEntrySCTable(T, 4, 1, [1, 4]);
SetEntrySCTable(T, 4, 2, [1, 3]);
SetEntrySCTable(T, 4, 3, [-1, 2]);
SetEntrySCTable(T, 4, 4, [-1, 1]);

A := AlgebraByStructureConstants(Rationals, T, ["e", "i", "j", "k"]);
b := GeneratorsOfAlgebra(A);

IsAssociative(A);
# true

IsCommutative(A);
# false

# Then, like above

q := [1, 2, 3, 4]*b;
# e+(2)*i+(3)*j+(4)*k

# However, as is, GAP does not know division or conjugate on this algebra.
# QuaternionAlgebra is useful as well for extensions of rationals,
# and this one _has_ conjugate and division, as seen previously.

# Try this on Q[z] where z is the square root of 5 (in GAP it's ER(5))
F := FieldByGenerators([ER(5)]);
A := QuaternionAlgebra(F);
b := GeneratorsOfAlgebra(A);

q := [1, 2, 3, 4]*b;
# e+(2)*i+(3)*j+(4)*k

# Conjugate and division

ComplexConjugate(q);
# e+(-2)*i+(-3)*j+(-4)*k

1/q;
# (1/30)*e+(-1/15)*i+(-1/10)*j+(-2/15)*k


## Go

Conventions for method receiver, parameter, and return values modeled after Go's big number package. It provides flexibility without requiring unnecessary object creation. The test program creates only four quaternion objects, the three inputs and one more for an output. The three inputs are reused repeatedly without being modified. The output is also reused repeatedly, being overwritten for each operation.

package main

import (
"fmt"
"math"
)

type qtn struct {
r, i, j, k float64
}

var (
q  = &qtn{1, 2, 3, 4}
q1 = &qtn{2, 3, 4, 5}
q2 = &qtn{3, 4, 5, 6}

r  float64 = 7
)

func main() {
fmt.Println("Inputs")
fmt.Println("q:", q)
fmt.Println("q1:", q1)
fmt.Println("q2:", q2)
fmt.Println("r:", r)

var qr qtn
fmt.Println("\nFunctions")
fmt.Println("q.norm():", q.norm())
fmt.Println("neg(q):", qr.neg(q))
fmt.Println("conj(q):", qr.conj(q))
fmt.Println("mulF(q, r):", qr.mulF(q, r))
fmt.Println("mulQ(q1, q2):", qr.mulQ(q1, q2))
fmt.Println("mulQ(q2, q1):", qr.mulQ(q2, q1))
}

func (q *qtn) String() string {
return fmt.Sprintf("(%g, %g, %g, %g)", q.r, q.i, q.j, q.k)
}

func (q *qtn) norm() float64 {
return math.Sqrt(q.r*q.r + q.i*q.i + q.j*q.j + q.k*q.k)
}

func (z *qtn) neg(q *qtn) *qtn {
z.r, z.i, z.j, z.k = -q.r, -q.i, -q.j, -q.k
return z
}

func (z *qtn) conj(q *qtn) *qtn {
z.r, z.i, z.j, z.k = q.r, -q.i, -q.j, -q.k
return z
}

func (z *qtn) addF(q *qtn, r float64) *qtn {
z.r, z.i, z.j, z.k = q.r+r, q.i, q.j, q.k
return z
}

func (z *qtn) addQ(q1, q2 *qtn) *qtn {
z.r, z.i, z.j, z.k = q1.r+q2.r, q1.i+q2.i, q1.j+q2.j, q1.k+q2.k
return z
}

func (z *qtn) mulF(q *qtn, r float64) *qtn {
z.r, z.i, z.j, z.k = q.r*r, q.i*r, q.j*r, q.k*r
return z
}

func (z *qtn) mulQ(q1, q2 *qtn) *qtn {
z.r, z.i, z.j, z.k =
q1.r*q2.r-q1.i*q2.i-q1.j*q2.j-q1.k*q2.k,
q1.r*q2.i+q1.i*q2.r+q1.j*q2.k-q1.k*q2.j,
q1.r*q2.j-q1.i*q2.k+q1.j*q2.r+q1.k*q2.i,
q1.r*q2.k+q1.i*q2.j-q1.j*q2.i+q1.k*q2.r
return z
}

Output:
Inputs
q: (1, 2, 3, 4)
q1: (2, 3, 4, 5)
q2: (3, 4, 5, 6)
r: 7

Functions
q.norm(): 5.477225575051661
neg(q): (-1, -2, -3, -4)
conj(q): (1, -2, -3, -4)
addF(q, r): (8, 2, 3, 4)
addQ(q1, q2): (5, 7, 9, 11)
mulF(q, r): (7, 14, 21, 28)
mulQ(q1, q2): (-56, 16, 24, 26)
mulQ(q2, q1): (-56, 18, 20, 28)


import Control.Monad (join)

data Quaternion a =
Q a a a a
deriving (Show, Eq)

realQ :: Quaternion a -> a
realQ (Q r _ _ _) = r

imagQ :: Quaternion a -> [a]
imagQ (Q _ i j k) = [i, j, k]

quaternionFromScalar :: (Num a) => a -> Quaternion a
quaternionFromScalar s = Q s 0 0 0

listFromQ :: Quaternion a -> [a]
listFromQ (Q a b c d) = [a, b, c, d]

quaternionFromList :: [a] -> Quaternion a
quaternionFromList [a, b, c, d] = Q a b c d

normQ :: (RealFloat a) => Quaternion a -> a
normQ = sqrt . sum . join (zipWith (*)) . listFromQ

conjQ :: (Num a) => Quaternion a -> Quaternion a
conjQ (Q a b c d) = Q a (-b) (-c) (-d)

instance (RealFloat a) => Num (Quaternion a) where
(Q a b c d) + (Q p q r s) = Q (a + p) (b + q) (c + r) (d + s)
(Q a b c d) - (Q p q r s) = Q (a - p) (b - q) (c - r) (d - s)
(Q a b c d) * (Q p q r s) =
Q
(a * p - b * q - c * r - d * s)
(a * q + b * p + c * s - d * r)
(a * r - b * s + c * p + d * q)
(a * s + b * r - c * q + d * p)
negate (Q a b c d)        = Q (-a) (-b) (-c) (-d)
abs q                     = quaternionFromScalar (normQ q)
signum (Q 0 0 0 0)        = 0
signum q@(Q a b c d)      = Q (a/n) (b/n) (c/n) (d/n) where n = normQ q
fromInteger n             = quaternionFromScalar (fromInteger n)

main :: IO ()
main = do
let q, q1, q2 :: Quaternion Double
q  = Q 1 2 3 4
q1 = Q 2 3 4 5
q2 = Q 3 4 5 6
print $(Q 0 1 0 0) * (Q 0 0 1 0) * (Q 0 0 0 1) -- i*j*k; prints "Q (-1.0) 0.0 0.0 0.0" print$ q1 * q2                                 -- prints "Q (-56.0) 16.0 24.0 26.0"
print $q2 * q1 -- prints "Q (-56.0) 18.0 20.0 28.0" print$ q1 * q2 == q2 * q1                      -- prints "False"
print $imagQ q -- prints "[2.0,3.0,4.0]"  ## Icon and Unicon Using Unicon's class system. class Quaternion(a, b, c, d) method norm () return sqrt (a*a + b*b + c*c + d*d) end method negative () return Quaternion(-a, -b, -c, -d) end method conjugate () return Quaternion(a, -b, -c, -d) end method add (n) if type(n) == "Quaternion__state" then return Quaternion(a+n.a, b+n.b, c+n.c, d+n.d) else return Quaternion(a+n, b, c, d) end method multiply (n) if type(n) == "Quaternion__state" then return Quaternion(a*n.a - b*n.b - c*n.c - d*n.d, a*n.b + b*n.a + c*n.d - d*n.c, a*n.c - b*n.d + c*n.a + d*n.b, a*n.d + b*n.c - c*n.b + d*n.a) else return Quaternion(a*n, b*n, c*n, d*n) end method sign (n) return if n >= 0 then "+" else "-" end method string () return ("" || a || sign(b) || abs(b) || "i" || sign(c) || abs(c) || "j" || sign(d) || abs(d) || "k"); end initially(a, b, c, d) self.a := if /a then 0 else a self.b := if /b then 0 else b self.c := if /c then 0 else c self.d := if /d then 0 else d end  To test the above: procedure main () q := Quaternion (1,2,3,4) q1 := Quaternion (2,3,4,5) q2 := Quaternion (3,4,5,6) r := 7 write ("The norm of " || q.string() || " is " || q.norm ()) write ("The negative of " || q.string() || " is " || q.negative().string ()) write ("The conjugate of " || q.string() || " is " || q.conjugate().string ()) write ("Sum of " || q.string() || " and " || r || " is " || q.add(r).string ()) write ("Sum of " || q.string() || " and " || q1.string() || " is " || q.add(q1).string ()) write ("Product of " || q.string() || " and " || r || " is " || q.multiply(r).string ()) write ("Product of " || q.string() || " and " || q1.string() || " is " || q.multiply(q1).string ()) write ("q1*q2 = " || q1.multiply(q2).string ()) write ("q2*q1 = " || q2.multiply(q1).string ()) end  Output: The norm of 1+2i+3j+4k is 5.477225575 The negative of 1+2i+3j+4k is -1-2i-3j-4k The conjugate of 1+2i+3j+4k is 1-2i-3j-4k Sum of 1+2i+3j+4k and 7 is 8+2i+3j+4k Sum of 1+2i+3j+4k and 2+3i+4j+5k is 3+5i+7j+9k Product of 1+2i+3j+4k and 7 is 7+14i+21j+28k Product of 1+2i+3j+4k and 2+3i+4j+5k is -36+6i+12j+12k q1*q2 = -56+16i+24j+26k q2*q1 = -56+18i+20j+28k  ## Idris With dependent types we can implement the more general Cayley-Dickson construction. Here the dependent type CD n a is implemented. It depends on a natural number n, which is the number of iterations carried out, and the base type a. So the real numbers are just CD 0 Double, the complex numbers CD 1 Double and the quaternions CD 2 Double module CayleyDickson data CD : Nat -> Type -> Type where CDBase : a -> CD 0 a CDProd : CD n a -> CD n a -> CD (S n) a pairTy : Nat -> Type -> Type pairTy Z a = a pairTy (S n) a = let b = pairTy n a in (b, b) fromPair : (n : Nat) -> pairTy n a -> CD n a fromPair Z x = CDBase x fromPair (S m) (x, y) = CDProd (fromPair m x)$ fromPair m y

toPair : CD n a -> pairTy n a
toPair (CDBase x) = x
toPair (CDProd x v) = (toPair x, toPair v)

first : CD n a -> a
first (CDBase x) = x
first (CDProd x v) = first x

fromBase : Num a => (n : Nat) -> a -> CD n a
fromBase Z x = CDBase x
fromBase (S m) x = CDProd (fromBase m x) $fromBase m 0 multSclr : Num a => CD n a -> a -> CD n a multSclr (CDBase x) y = CDBase$ x * y
multSclr (CDProd x v) y = CDProd (multSclr x y) $multSclr v y divSclr : Fractional a => CD n a -> a -> CD n a divSclr (CDBase x) y = CDBase$ x / y
divSclr (CDProd x v) y = CDProd (divSclr x y) $divSclr v y plusCD : Num a => CD n a -> CD n a -> CD n a plusCD (CDBase x) (CDBase y) = CDBase$ x + y
plusCD (CDProd x v) (CDProd y w) = CDProd (plusCD x y) $plusCD v w negCD : Neg a => CD n a -> CD n a negCD (CDBase x) = CDBase$ negate x
negCD (CDProd x v) = CDProd (negCD x) $negCD v minusCD : Neg a => CD n a -> CD n a -> CD n a minusCD (CDBase x) (CDBase y) = CDBase$ x - y
minusCD (CDProd x v) (CDProd y w) = CDProd (minusCD x y) $minusCD v w conjCD : Neg a => CD n a -> CD n a conjCD (CDBase x) = CDBase x conjCD (CDProd x v) = CDProd (conjCD x)$ negCD v

multCD : Neg a => CD n a -> CD n a -> CD n a
multCD (CDBase x) (CDBase y) = CDBase $x * y multCD (CDProd x v) (CDProd y w) = CDProd (minusCD (multCD x y) (multCD (conjCD w) v))$ plusCD (multCD w x) $multCD v$ conjCD y

absSqrCD : Neg a => CD n a -> CD n a
absSqrCD x = multCD x $conjCD x sqrLnCD : Neg a => CD n a -> a sqrLnCD = first . absSqrCD recipCD : Neg a => Fractional a => CD n a -> CD n a recipCD x = conjCD$ divSclr x $sqrLnCD x divCD : Neg a => Fractional a => CD n a -> CD n a -> CD n a divCD x y = multCD x$ recipCD y

absCD : CD n Double -> Double
absCD x = sqrt $sqrLnCD x showComps : Show a => CD n a -> String showComps (CDBase x) = show x showComps (CDProd x v) = showComps x ++ ", " ++ showComps v Eq a => Eq (CD n a) where (CDBase x) == (CDBase y) = x == y (CDProd x v) == (CDProd y w) = x == y && v == w Show a => Show (CD n a) where show x = "(" ++ showComps x ++ ")" Neg a => Num (CD n a) where (+) = plusCD (*) = multCD fromInteger m {n} = fromBase n$ fromInteger m

Neg a => Neg (CD n a) where
negate = negCD
(-) = minusCD

(Neg a, Fractional a) => Fractional (CD n a) where
(/) = divCD
recip = recipCD

Abs (CD n Double) where
abs {n} = fromBase n . absCD


To test it:

import CayleyDickson

main : IO ()
main =
do
let q = fromPair 2 ((1, 2), (3, 4))
let q1 = fromPair 2 ((2, 3), (4, 5))
let q2 = fromPair 2 ((3, 4), (5, 6))
printLn $q1 * q2 printLn$ q2 * q1
printLn $q1 * q2 == q2 * q1  ## J Derived from the j wiki:  NB. utilities ip=: +/ .* NB. inner product T=. (_1^#:0 10 9 12)*0 7 16 23 A.=i.4 toQ=: 4&{."1 :[: NB. real scalars -> quaternion NB. task norm=: %:@ip~@toQ NB. | y neg=: -&toQ NB. - y and x - y conj=: 1 _1 _1 _1 * toQ NB. + y add=: +&toQ NB. x + y mul=: (ip T ip ])&toQ NB. x * y  T is a rank 3 tensor which allows us to express quaternion product ab as the inner product ATB if A and B are 4 element vectors representing the quaternions a and b. (Note also that once we have defined mul we no longer need to retain the definition of T, so we define T using =. instead of =:). The value of T is probably more interesting than its definition, so:  T 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 0 _1 0 0 1 0 0 0 0 0 0 _1 0 0 1 0 0 0 _1 0 0 0 0 1 1 0 0 0 0 _1 0 0 0 0 0 _1 0 0 _1 0 0 1 0 0 1 0 0 0  In other words, the last dimension of T corresponds to the structure of the right argument (columns, in the display of T), the first dimension of T corresponds to the structure of the left argument (tables, in the display of T) and the middle dimension of T corresponds to the structure of the result (rows, in the display of T). Example use:  q=: 1 2 3 4 q1=: 2 3 4 5 q2=: 3 4 5 6 r=: 7 norm q 5.47723 neg q _1 _2 _3 _4 conj q 1 _2 _3 _4 r add q 8 2 3 4 q1 add q2 5 7 9 11 r mul q 7 14 21 28 q1 mul q2 _56 16 24 26 q2 mul q1 _56 18 20 28  Finally, note that when quaternions are used to represent orientation or rotation, we are typically only interested in unit length quaternions. As this is the typical application for quaternions, you will sometimes see quaternion multiplication expressed using "simplifications" which are only valid for unit length quaternions. But note also that in many of those contexts you also need to normalize the quaternion length after multiplication. (An exception to this need to normalize unit length quaternions after multiplication might be when quaternions are represented as an index into a geodesic grid. For example, a grid with 16x20 faces would have a total of 15 vertices for each face (5+4+3+2+1), 3 of those vertices would be from the original 20 vertices of the icosahedron, and 9 of those vertices (5+4+3-3) would be on the edge of the original face (and, thus, used for two faces), the remaining 3 vertices would be interior. This means we would have 170 vertices (20+(20*9%2)+20*3, which would allow a quaternion to be represented in a single byte index into a list of 170 quaternions, and would allow quaternion multiplication to be represented as a 29kbyte lookup table. In some contexts - where quaternion multiplication is needed in high volume for secondary or tertiary issues (where precision isn't vital), such low accuracy quaternions might be adequate or even an advantage...) ## Java public class Quaternion { private final double a, b, c, d; public Quaternion(double a, double b, double c, double d) { this.a = a; this.b = b; this.c = c; this.d = d; } public Quaternion(double r) { this(r, 0.0, 0.0, 0.0); } public double norm() { return Math.sqrt(a * a + b * b + c * c + d * d); } public Quaternion negative() { return new Quaternion(-a, -b, -c, -d); } public Quaternion conjugate() { return new Quaternion(a, -b, -c, -d); } public Quaternion add(double r) { return new Quaternion(a + r, b, c, d); } public static Quaternion add(Quaternion q, double r) { return q.add(r); } public static Quaternion add(double r, Quaternion q) { return q.add(r); } public Quaternion add(Quaternion q) { return new Quaternion(a + q.a, b + q.b, c + q.c, d + q.d); } public static Quaternion add(Quaternion q1, Quaternion q2) { return q1.add(q2); } public Quaternion times(double r) { return new Quaternion(a * r, b * r, c * r, d * r); } public static Quaternion times(Quaternion q, double r) { return q.times(r); } public static Quaternion times(double r, Quaternion q) { return q.times(r); } public Quaternion times(Quaternion q) { return new Quaternion( a * q.a - b * q.b - c * q.c - d * q.d, a * q.b + b * q.a + c * q.d - d * q.c, a * q.c - b * q.d + c * q.a + d * q.b, a * q.d + b * q.c - c * q.b + d * q.a ); } public static Quaternion times(Quaternion q1, Quaternion q2) { return q1.times(q2); } @Override public boolean equals(Object obj) { if (!(obj instanceof Quaternion)) return false; final Quaternion other = (Quaternion) obj; if (Double.doubleToLongBits(this.a) != Double.doubleToLongBits(other.a)) return false; if (Double.doubleToLongBits(this.b) != Double.doubleToLongBits(other.b)) return false; if (Double.doubleToLongBits(this.c) != Double.doubleToLongBits(other.c)) return false; if (Double.doubleToLongBits(this.d) != Double.doubleToLongBits(other.d)) return false; return true; } @Override public String toString() { return String.format("%.2f + %.2fi + %.2fj + %.2fk", a, b, c, d).replaceAll("\\+ -", "- "); } public String toQuadruple() { return String.format("(%.2f, %.2f, %.2f, %.2f)", a, b, c, d); } public static void main(String[] args) { Quaternion q = new Quaternion(1.0, 2.0, 3.0, 4.0); Quaternion q1 = new Quaternion(2.0, 3.0, 4.0, 5.0); Quaternion q2 = new Quaternion(3.0, 4.0, 5.0, 6.0); double r = 7.0; System.out.format("q = %s%n", q); System.out.format("q1 = %s%n", q1); System.out.format("q2 = %s%n", q2); System.out.format("r = %.2f%n%n", r); System.out.format("\u2016q\u2016 = %.2f%n", q.norm()); System.out.format("-q = %s%n", q.negative()); System.out.format("q* = %s%n", q.conjugate()); System.out.format("q + r = %s%n", q.add(r)); System.out.format("q1 + q2 = %s%n", q1.add(q2)); System.out.format("q \u00d7 r = %s%n", q.times(r)); Quaternion q1q2 = q1.times(q2); Quaternion q2q1 = q2.times(q1); System.out.format("q1 \u00d7 q2 = %s%n", q1q2); System.out.format("q2 \u00d7 q1 = %s%n", q2q1); System.out.format("q1 \u00d7 q2 %s q2 \u00d7 q1%n", (q1q2.equals(q2q1) ? "=" : "\u2260")); } }  Output: q = 1.00 + 2.00i + 3.00j + 4.00k q1 = 2.00 + 3.00i + 4.00j + 5.00k q2 = 3.00 + 4.00i + 5.00j + 6.00k r = 7.00 ‖q‖ = 5.48 -q = -1.00 - 2.00i - 3.00j - 4.00k q* = 1.00 - 2.00i - 3.00j - 4.00k q + r = 8.00 + 2.00i + 3.00j + 4.00k q1 + q2 = 5.00 + 7.00i + 9.00j + 11.00k q × r = 7.00 + 14.00i + 21.00j + 28.00k q1 × q2 = -56.00 + 16.00i + 24.00j + 26.00k q2 × q1 = -56.00 + 18.00i + 20.00j + 28.00k q1 × q2 ≠ q2 × q1 ## JavaScript Runs on Firefox 3+, limited support in other JS engines. More compatible JavaScript deserves its own entry. var Quaternion = (function() { // The Q() function takes an array argument and changes it // prototype so that it becomes a Quaternion instance. This is // scoped only for prototype member access. function Q(a) { a.__proto__ = proto; return a; } // Actual constructor. This constructor converts its arguments to // an array, then that array to a Quaternion instance, then // returns that instance. (using "new" with this constructor is // optional) function Quaternion() { return Q(Array.prototype.slice.call(arguments, 0, 4)); } // Prototype for all Quaternions const proto = { // Inherits from a 4-element Array __proto__ : [0,0,0,0], // Properties -- In addition to Array[0..3] access, we // also define matching a, b, c, and d properties get a() this[0], get b() this[1], get c() this[2], get d() this[3], // Methods norm : function() Math.sqrt(this.map(function(x) x*x).reduce(function(x,y) x+y)), negate : function() Q(this.map(function(x) -x)), conjugate : function() Q([ this[0] ].concat(this.slice(1).map(function(x) -x))), add : function(x) { if ("number" === typeof x) { return Q([ this[0] + x ].concat(this.slice(1))); } else { return Q(this.map(function(v,i) v+x[i])); } }, mul : function(r) { var q = this; if ("number" === typeof r) { return Q(q.map(function(e) e*r)); } else { return Q([ q[0] * r[0] - q[1] * r[1] - q[2] * r[2] - q[3] * r[3], q[0] * r[1] + q[1] * r[0] + q[2] * r[3] - q[3] * r[2], q[0] * r[2] - q[1] * r[3] + q[2] * r[0] + q[3] * r[1], q[0] * r[3] + q[1] * r[2] - q[2] * r[1] + q[3] * r[0] ]); } }, equals : function(q) this.every(function(v,i) v === q[i]), toString : function() (this[0] + " + " + this[1] + "i + "+this[2] + "j + " + this[3] + "k").replace(/\+ -/g, '- ') }; Quaternion.prototype = proto; return Quaternion; })();  Task/Example Usage: var q = Quaternion(1,2,3,4); var q1 = Quaternion(2,3,4,5); var q2 = Quaternion(3,4,5,6); var r = 7; console.log("q = "+q); console.log("q1 = "+q1); console.log("q2 = "+q2); console.log("r = "+r); console.log("1. q.norm() = "+q.norm()); console.log("2. q.negate() = "+q.negate()); console.log("3. q.conjugate() = "+q.conjugate()); console.log("4. q.add(r) = "+q.add(r)); console.log("5. q1.add(q2) = "+q1.add(q2)); console.log("6. q.mul(r) = "+q.mul(r)); console.log("7.a. q1.mul(q2) = "+q1.mul(q2)); console.log("7.b. q2.mul(q1) = "+q2.mul(q1)); console.log("8. q1.mul(q2) " + (q1.mul(q2).equals(q2.mul(q1)) ? "==" : "!=") + " q2.mul(q1)");  Output: q = 1 + 2i + 3j + 4k q1 = 2 + 3i + 4j + 5k q2 = 3 + 4i + 5j + 6k r = 7 1. q.norm() = 5.477225575051661 2. q.negate() = -1 - 2i - 3j - 4k 3. q.conjugate() = 1 - 2i - 3j - 4k 4. q.add(r) = 8 + 2i + 3j + 4k 5. q1.add(q2) = 5 + 7i + 9j + 11k 6. q.mul(r) = 7 + 14i + 21j + 28k 7.a. q1.mul(q2) = -56 + 16i + 24j + 26k 7.b. q2.mul(q1) = -56 + 18i + 20j + 28k 8. q1.mul(q2) != q2.mul(q1) ## jq Program file: quaternion.jq def Quaternion(q0;q1;q2;q3): { "q0": q0, "q1": q1, "q2": q2, "q3": q3, "type": "Quaternion" }; # promotion of a real number to a quaternion def Quaternion(r): if (r|type) == "number" then Quaternion(r;0;0;0) else r end; # thoroughly recursive pretty-print def pp: def signage: if . >= 0 then "+ \(.)" else "- \(-.)" end; if type == "object" then if .type == "Quaternion" then "\(.q0) \(.q1|signage)i \(.q2|signage)j \(.q3|signage)k" else with_entries( {key, "value" : (.value|pp)} ) end elif type == "array" then map(pp) else . end ; def real(z): Quaternion(z).q0; # Note: imag(z) returns the "i" component only, # reflecting the embedding of the complex numbers within the quaternions: def imag(z): Quaternion(z).q1; def conj(z): Quaternion(z) | Quaternion(.q0; -(.q1); -(.q2); -(.q3)); def abs2(z): Quaternion(z) | .q0 * .q0 + .q1*.q1 + .q2*.q2 + .q3*.q3; def abs(z): abs2(z) | sqrt; def negate(z): Quaternion(z) | Quaternion(-.q0; -.q1; -.q2; -.q3); # z + w def plus(z; w): def plusq(z;w): Quaternion(z.q0 + w.q0; z.q1 + w.q1; z.q2 + w.q2; z.q3 + w.q3); plusq( Quaternion(z); Quaternion(w) ); # z - w def minus(z; w): def minusq(z;w): Quaternion(z.q0 - w.q0; z.q1 - w.q1; z.q2 - w.q2; z.q3 - w.q3); minusq( Quaternion(z); Quaternion(w) ); # * def times(z; w): def timesq(z; w): Quaternion(z.q0*w.q0 - z.q1*w.q1 - z.q2*w.q2 - z.q3*w.q3; z.q0*w.q1 + z.q1*w.q0 + z.q2*w.q3 - z.q3*w.q2; z.q0*w.q2 - z.q1*w.q3 + z.q2*w.q0 + z.q3*w.q1; z.q0*w.q3 + z.q1*w.q2 - z.q2*w.q1 + z.q3*w.q0); timesq( Quaternion(z); Quaternion(w) ); # (z/w) def div(z; w): if (w|type) == "number" then Quaternion(z.q0/w; z.q1/w; z.q2/w; z.q3/w) else times(z; inv(w)) end; def inv(z): div(conj(z); abs2(z)); # Example usage and output: def say(msg; e): "\(msg) => \(e|pp)"; def demo: say( "Quaternion(1;0;0;0)"; Quaternion(1;0;0;0)), (Quaternion (1; 2; 3; 4) as$q
| Quaternion(2; 3; 4; 5) as $q1 | Quaternion(3; 4; 5; 6) as$q2
| 7 as $r | say( "abs($q)";        abs($q) ), # norm say( "negate($q)";     negate($q) ), say( "conj($q)";       conj($q) ), "", say( "plus($r; $q)"; plus($r; $q)), say( "plus($q; $r)"; plus($q; $r)), "", say( "plus($q1; $q2 )"; plus($q1; $q2)), "", say( "times($r;$q)"; times($r;$q)), say( "times($q;$r)"; times($q;$r)), "", say( "times($q1;$q2)"; times($q1;$q2)), say( "times($q2; $q1)"; times($q2; $q1)), say( "times($q1; $q2) != times($q2; $q1)"; times($q1; $q2) != times($q2; $q1) ) ) ; demo Example usage and output: # jq -c -n -R -f quaternion.jq Quaternion(1;0;0;0) => 1 + 0i + 0j + 0k abs($q) => 5.477225575051661
negate($q) => -1 - 2i - 3j + -4k conj($q) => 1 - 2i - 3j - 4k

plus($r;$q) => 8 + 2i + 3j + 4k
plus($q;$r) => 8 + 2i + 3j + 4k

plus($q1;$q2 ) => 5 + 7i + 9j + 11k

times($r;$q) => 7 + 14i + 21j + 28k
times($q;$r) => 7 + 14i + 21j + 28k

times($q1;$q2) => -56 + 16i + 24j + 26k
times($q2;$q1) => -56 + 18i + 20j + 28k
times($q1;$q2) != times($q2;$q1) => true


## Julia

https://github.com/andrioni/Quaternions.jl/blob/master/src/Quaternions.jl has a more complete implementation. This is derived from the quaternion example file included with Julia 0.2, which implements a quaternion type complete with arithmetic, type conversions / promotion rules, polymorphism over arbitrary real numeric types, and pretty-printing.

import Base: convert, promote_rule, show, conj, abs, +, -, *

immutable Quaternion{T<:Real} <: Number
q0::T
q1::T
q2::T
q3::T
end

Quaternion(q0::Real,q1::Real,q2::Real,q3::Real) = Quaternion(promote(q0,q1,q2,q3)...)

convert{T}(::Type{Quaternion{T}}, x::Real) =
Quaternion(convert(T,x), zero(T), zero(T), zero(T))
convert{T}(::Type{Quaternion{T}}, z::Complex) =
Quaternion(convert(T,real(z)), convert(T,imag(z)), zero(T), zero(T))
convert{T}(::Type{Quaternion{T}}, z::Quaternion) =
Quaternion(convert(T,z.q0), convert(T,z.q1), convert(T,z.q2), convert(T,z.q3))

promote_rule{T,S}(::Type{Complex{T}}, ::Type{Quaternion{S}}) = Quaternion{promote_type(T,S)}
promote_rule{T<:Real,S}(::Type{T}, ::Type{Quaternion{S}}) = Quaternion{promote_type(T,S)}
promote_rule{T,S}(::Type{Quaternion{T}}, ::Type{Quaternion{S}}) = Quaternion{promote_type(T,S)}

function show(io::IO, z::Quaternion)
pm(x) = x <	0 ? " - $(-x)" : " +$x"
print(io, z.q0, pm(z.q1), "i", pm(z.q2), "j", pm(z.q3), "k")
end

conj(z::Quaternion) = Quaternion(z.q0, -z.q1, -z.q2, -z.q3)
abs(z::Quaternion) = sqrt(z.q0*z.q0 + z.q1*z.q1 + z.q2*z.q2 + z.q3*z.q3)

(-)(z::Quaternion) = Quaternion(-z.q0, -z.q1, -z.q2, -z.q3)

(+)(z::Quaternion, w::Quaternion) = Quaternion(z.q0 + w.q0, z.q1 + w.q1,
z.q2 + w.q2, z.q3 + w.q3)
(-)(z::Quaternion, w::Quaternion) = Quaternion(z.q0 - w.q0, z.q1 - w.q1,
z.q2 - w.q2, z.q3 - w.q3)
(*)(z::Quaternion, w::Quaternion) = Quaternion(z.q0*w.q0 - z.q1*w.q1 - z.q2*w.q2 - z.q3*w.q3,
z.q0*w.q1 + z.q1*w.q0 + z.q2*w.q3 - z.q3*w.q2,
z.q0*w.q2 - z.q1*w.q3 + z.q2*w.q0 + z.q3*w.q1,
z.q0*w.q3 + z.q1*w.q2 - z.q2*w.q1 + z.q3*w.q0)


Example usage and output:

julia> q = Quaternion(1,0,0,0)
julia> q  = Quaternion (1, 2, 3, 4)
q1 = Quaternion(2, 3, 4, 5)
q2 = Quaternion(3, 4, 5, 6)
r = 7.

julia> norm(q)
5.477225575051661

julia> -q
-1 - 2i - 3j - 4k

julia> conj(q)
1 - 2i - 3j - 4k

julia> r + q, q + r
(8.0 + 2.0i + 3.0j + 4.0k,8.0 + 2.0i + 3.0j + 4.0k)

julia> q1 + q2
5 + 7i + 9j + 11k

julia> r*q, q*r
(7.0 + 14.0i + 21.0j + 28.0k,7.0 + 14.0i + 21.0j + 28.0k)

julia> q1*q2, q2*q1, q1*q2 != q2*q1
(-56 + 16i + 24j + 26k,-56 + 18i + 20j + 28k,true)


## Kotlin

// version 1.1.2

data class Quaternion(val a: Double, val b: Double, val c: Double, val d: Double) {
operator fun plus(other: Quaternion): Quaternion {
return Quaternion (this.a + other.a, this.b + other.b,
this.c + other.c, this.d + other.d)
}

operator fun plus(r: Double) = Quaternion(a + r, b, c, d)

operator fun times(other: Quaternion): Quaternion {
return Quaternion(
this.a * other.a - this.b * other.b - this.c * other.c - this.d * other.d,
this.a * other.b + this.b * other.a + this.c * other.d - this.d * other.c,
this.a * other.c - this.b * other.d + this.c * other.a + this.d * other.b,
this.a * other.d + this.b * other.c - this.c * other.b + this.d * other.a
)
}

operator fun times(r: Double) = Quaternion(a * r, b * r, c * r, d * r)

operator fun unaryMinus() =  Quaternion(-a, -b, -c, -d)

fun conj() = Quaternion(a, -b, -c, -d)

fun norm() = Math.sqrt(a * a + b * b + c * c + d * d)

override fun toString() = "($a,$b, $c,$d)"
}

// extension functions for Double type
operator fun Double.plus(q: Quaternion) = q + this
operator fun Double.times(q: Quaternion) = q * this

fun main(args: Array<String>) {
val q  = Quaternion(1.0, 2.0, 3.0, 4.0)
val q1 = Quaternion(2.0, 3.0, 4.0, 5.0)
val q2 = Quaternion(3.0, 4.0, 5.0, 6.0)
val r  = 7.0
println("q  = $q") println("q1 =$q1")
println("q2 = $q2") println("r =$r\n")
println("norm(q) = ${"%f".format(q.norm())}") println("-q =${-q}")
println("conj(q) = ${q.conj()}\n") println("r + q =${r + q}")
println("q  + r  = ${q + r}") println("q1 + q2 =${q1 + q2}\n")
println("r  * q  = ${r * q}") println("q * r =${q * r}")
val q3 = q1 * q2
val q4 = q2 * q1
println("q1 * q2 = $q3") println("q2 * q1 =$q4\n")
println("q1 * q2 != q2 * q1 = ${q3 != q4}") }  Output: q = (1.0, 2.0, 3.0, 4.0) q1 = (2.0, 3.0, 4.0, 5.0) q2 = (3.0, 4.0, 5.0, 6.0) r = 7.0 norm(q) = 5.477226 -q = (-1.0, -2.0, -3.0, -4.0) conj(q) = (1.0, -2.0, -3.0, -4.0) r + q = (8.0, 2.0, 3.0, 4.0) q + r = (8.0, 2.0, 3.0, 4.0) q1 + q2 = (5.0, 7.0, 9.0, 11.0) r * q = (7.0, 14.0, 21.0, 28.0) q * r = (7.0, 14.0, 21.0, 28.0) q1 * q2 = (-56.0, 16.0, 24.0, 26.0) q2 * q1 = (-56.0, 18.0, 20.0, 28.0) q1 * q2 != q2 * q1 = true  ## Liberty BASIC Quaternions saved as a space-separated string of four numbers.  q$ = q$( 1 , 2 , 3 , 4 ) q1$ = q$( 2 , 3 , 4 , 5 ) q2$ = q$( 3 , 4 , 5 , 6 ) real = 7 print "q = " ; q$
print "q1 = " ; q1$print "q2 = " ; q2$

print "real = " ; real

print "length /norm q  = " ; length( q$) ' =norm norm of q print "negative (-q1) = " ; negative$( q1$) ' =negative negated q1 print "conjugate q = " ; conjugate$( q$) ' conjugate conjugate q print "real + q = " ; add1$( q$, real ) ' real +quaternion real +q print "q + q2 = " ; add2$( q$, q2$ )          '   sum two quaternions          q +q2
print "real * q        = " ; multiply1$( q$ , real )    '   real *quaternion             real *q
print "q1 * q2         = " ; multiply2$( q1$ , q2$) ' product of two quaternions q1 & q2 print "q2 * q1 = " ; multiply2$( q2$, q1$ )    '   show q1 *q2 <> q2 *q1

end

function q$( r , i , j , k ) q$ = str$( r); " "; str$( i); " "; str$( j); " "; str$( k)
end function

function length( q$) r = val( word$( q$, 1 ) ) i = val( word$( q$, 2 ) ) j = val( word$( q$, 3 ) ) k = val( word$( q$, 4 ) ) length =sqr( r^2 +i^2 +j^2 +k^2) end function function multiply1$( q$, d ) r = val( word$( q$, 1 ) ) i = val( word$( q$, 2 ) ) j = val( word$( q$, 3 ) ) k = val( word$( q$, 4 ) ) multiply1$ =q$( r*d, i*d, j*d, k*d) end function function multiply2$( q$, b$ )
ar = val( word$( q$ , 1 ) )   'a1
ai = val( word$( q$ , 2 ) )   'b1
aj = val( word$( q$ , 3 ) )   'c1
ak = val( word$( q$ , 4 ) )   'd1

br = val( word$( b$ , 1 ) )   'a2
bi = val( word$( b$ , 2 ) )   'b2
bj = val( word$( b$ , 3 ) )   'c2
bk = val( word$( b$ , 4 ) )   'd2

multiply2$=q$( _
ar *br_
+( 0 -ai) *bi_
+( 0 -aj) *bj_
+( 0 -ak) *bk _
,_
ar *bi_
+ai *br_
+aj *bk_
+( 0 -ak) *bj_
,_
ar *bj_
+( 0 -ai) *bk_
+aj *br_
+ak *bi_
,_
ar *bk_
+ai *bj_
+( 0 -aj) *bi_
+ak *br )
end function

function negative$( q$ )
r = val( word$( q$ , 1 ) )
i = val( word$( q$ , 2 ) )
j = val( word$( q$ , 3 ) )
k = val( word$( q$ , 4 ) )
negative$=q$( 0-r, 0-i, 0-j, 0-k)
end function

function conjugate$( q$ )
r = val( word$( q$ , 1 ) )
i = val( word$( q$ , 2 ) )
j = val( word$( q$ , 3 ) )
k = val( word$( q$ , 4 ) )
conjugate$=q$( r, 0-i, 0-j, 0-k)
end function

function add1$( q$ , real )
r = val( word$( q$ , 1 ) )
i = val( word$( q$ , 2 ) )
j = val( word$( q$ , 3 ) )
k = val( word$( q$ , 4 ) )
add1$=q$( r +real, i, j, k)
end function

function add2$( q$ , b$) ar = val( word$( q$, 1 ) ) ai = val( word$( q$, 2 ) ) aj = val( word$( q$, 3 ) ) ak = val( word$( q$, 4 ) ) br = val( word$( b$, 1 ) ) bi = val( word$( b$, 2 ) ) bj = val( word$( b$, 3 ) ) bk = val( word$( b$, 4 ) ) add2$ =q$( ar +br, ai +bi, aj +bj, ak +bk) end function ## Lua Quaternion = {} function Quaternion.new( a, b, c, d ) local q = { a = a or 1, b = b or 0, c = c or 0, d = d or 0 } local metatab = {} setmetatable( q, metatab ) metatab.__add = Quaternion.add metatab.__sub = Quaternion.sub metatab.__unm = Quaternion.unm metatab.__mul = Quaternion.mul return q end function Quaternion.add( p, q ) if type( p ) == "number" then return Quaternion.new( p+q.a, q.b, q.c, q.d ) elseif type( q ) == "number" then return Quaternion.new( p.a+q, p.b, p.c, p.d ) else return Quaternion.new( p.a+q.a, p.b+q.b, p.c+q.c, p.d+q.d ) end end function Quaternion.sub( p, q ) if type( p ) == "number" then return Quaternion.new( p-q.a, q.b, q.c, q.d ) elseif type( q ) == "number" then return Quaternion.new( p.a-q, p.b, p.c, p.d ) else return Quaternion.new( p.a-q.a, p.b-q.b, p.c-q.c, p.d-q.d ) end end function Quaternion.unm( p ) return Quaternion.new( -p.a, -p.b, -p.c, -p.d ) end function Quaternion.mul( p, q ) if type( p ) == "number" then return Quaternion.new( p*q.a, p*q.b, p*q.c, p*q.d ) elseif type( q ) == "number" then return Quaternion.new( p.a*q, p.b*q, p.c*q, p.d*q ) else return Quaternion.new( p.a*q.a - p.b*q.b - p.c*q.c - p.d*q.d, p.a*q.b + p.b*q.a + p.c*q.d - p.d*q.c, p.a*q.c - p.b*q.d + p.c*q.a + p.d*q.b, p.a*q.d + p.b*q.c - p.c*q.b + p.d*q.a ) end end function Quaternion.conj( p ) return Quaternion.new( p.a, -p.b, -p.c, -p.d ) end function Quaternion.norm( p ) return math.sqrt( p.a^2 + p.b^2 + p.c^2 + p.d^2 ) end function Quaternion.print( p ) print( string.format( "%f + %fi + %fj + %fk\n", p.a, p.b, p.c, p.d ) ) end  Examples: q1 = Quaternion.new( 1, 2, 3, 4 ) q2 = Quaternion.new( 5, 6, 7, 8 ) r = 12 print( "norm(q1) = ", Quaternion.norm( q1 ) ) io.write( "-q1 = " ); Quaternion.print( -q1 ) io.write( "conj(q1) = " ); Quaternion.print( Quaternion.conj( q1 ) ) io.write( "r+q1 = " ); Quaternion.print( r+q1 ) io.write( "q1+r = " ); Quaternion.print( q1+r ) io.write( "r*q1 = " ); Quaternion.print( r*q1 ) io.write( "q1*r = " ); Quaternion.print( q1*r ) io.write( "q1*q2 = " ); Quaternion.print( q1*q2 ) io.write( "q2*q1 = " ); Quaternion.print( q2*q1 )  Output: norm(q1) = 5.4772255750517 -q1 = -1.000000 -2.000000i -3.000000j -4.000000k conj(q1) = 1.000000 -2.000000i -3.000000j -4.000000k r+q1 = 13.000000 + 2.000000i + 3.000000j + 4.000000k q1+r = 13.000000 + 2.000000i + 3.000000j + 4.000000k r*q1 = 12.000000 + 24.000000i + 36.000000j + 48.000000k q1*r = 12.000000 + 24.000000i + 36.000000j + 48.000000k q1*q2 = -60.000000 + 12.000000i + 30.000000j + 24.000000k q2*q1 = -60.000000 + 20.000000i + 14.000000j + 32.000000k ## M2000 Interpreter We can define Quaternions using a class, using operators for specific tasks, as negate, add, multiplication and equality with rounding to 13 decimal place (thats what doing "==" operator for doubles) Module CheckIt { class Quaternion { \\ by default are double a,b,c,d Property ToString$ {
Value {
link parent a,b,c, d to a,b,c,d
value$=format$("{0} + {1}i + {2}j + {3}k",a,b,c,d)
}
}
Property Norm { Value}
Operator "==" {
push .a==n.a and .b==n.b and .c==n.c and .d==n.d
}
Module CalcNorm {
.[Norm]<=sqrt(.a**2+.b**2+.c**2+.d**2)
}
Operator Unary {
.a-! : .b-! : .c-! :.d-!
}
Function Conj {
q=this
for q {
.b-! : .c-! :.d-!
}
=q
}
q=this
for q {
.a+=Number : .CalcNorm
}
=q
}
Operator "+"  {
For this, q2 {
.a+=..a :.b+=..b:.c+=..c:.d+=..d
.CalcNorm
}
}
Function Mul(r)  {
q=this
for q {
.a*=r:.b*=r:.c*=r:.d*=r:.CalcNorm
}
=q
}
Operator "*" {
For This, q2 {
Push .a*..a-.b*..b-.c*..c-.d*..d
Push .a*..b+.b*..a+.c*..d-.d*..c
Push .a*..c-.b*..d+.c*..a+.d*..b
.d<=.a*..d+.b*..c-.c*..b+.d*..a
.CalcNorm
}
}
class:
module Quaternion {
if match("NNNN") then {
.CalcNorm
}
}
}
\\ variables
r=7
q=Quaternion(1,2,3,4)
q1=Quaternion(2,3,4,5)
q2=Quaternion(3,4,5,6)

\\ perform negate, conjugate, multiply by real, add a real, multiply quanterions, multiply in reverse order
qneg=-q
qconj=q.conj()
qmul=q.Mul(r)
q1q2=q1*q2
q2q1=q2*q1

Print "q = ";q.ToString$Print "Normal q = ";q.Norm Print "Neg q = ";qneg.ToString$
Print "Conj q = ";qconj.ToString$Print "Mul q 7 = ";qmul.ToString$
Print "Add q 7 = ";qadd.ToString$Print "q1 = ";q1.ToString$
Print "q2 = ";q2.ToString$Print "q1 * q2 = ";q1q2.ToString$
Print "q2 * q1 = ";q2q1.ToString$Print q1==q1 ' true Print q1q2==q2q1 ' false \\ multiplication and equality in one expression Print q1 * q2 == q2 * q1 ' false Print q1 * q2 == q1 * q2 ' true } CheckIt Output: q = 1 + 2i + 3j + 4k Normal q = 5.47722557505166 Neg q = -1 + -2i + -3j + -4k Conj q = 1 + -2i + -3j + -4k Mul q 7 = 7 + 14i + 21j + 28k Add q 7 = 8 + 2i + 3j + 4k q1 = 2 + 3i + 4j + 5k q2 = 3 + 4i + 5j + 6k q1 * q2 = -56 + 16i + 24j + 26k q2 * q1 = -56 + 18i + 20j + 28k True False false True ## Maple with(ArrayTools); module Quaternion() option object; local real := 0; local i := 0; local j := 0; local k := 0; export getReal::static := proc(self::Quaternion,$)
return self:-real;
end proc;

export getI::static := proc(self::Quaternion, $) return self:-i; end proc; export getJ::static := proc(self::Quaternion,$)
return self:-j;
end proc;

export getK::static := proc(self::Quaternion, $) return self:-k; end proc; export Norm::static := proc(self::Quaternion,$)
return sqrt(self:-real^2 + self:-i^2 + self:-j^2 + self:-k^2);
end proc;

# NegativeQuaternion returns the additive inverse of the quaternion
export NegativeQuaternion::static := proc(self::Quaternion, $) return Quaternion(- self:-real, - self:-i, - self:-j, - self:-k); end proc; export Conjugate::static := proc(self::Quaternion,$)
return Quaternion(self:-real, - self:-i, - self:-j, - self:-k);
end proc;

export +::static := overload ([
return Quaternion(self:-real + getReal(x), self:-i + getI(x), self:-j + getJ(x), self:-k + getK(x));
end proc,
return Quaternion(self:-real + x, self:-i, self:-j, self:-k);
end proc,
return Quaternion(x + self:-real, self:-i, self:-j, self:-k);
end
]);

# convert quaternion to additive inverse
export -::static := overload([
return Quaternion(-self:-real, -self:-i, -self:-j, -self:-k);
end
]);

# quaternion multiplication is non-abelian so the . operator needs to be used
export .::static := overload([
return Quaternion(self:-real * getReal(x) - self:-i * getI(x) - self:-j * getJ(x) - self:-k * getK(x),
self:-real * getI(x) + self:-i * getReal(x) + self:-j * getK(x) - self:-k * getJ(x),
self:-real * getJ(x) + self:-j * getReal(x) - self:-i * getK(x) + self:-k * getI(x),
self:-real * getK(x) + self:-k * getReal(x) + self:-i * getJ(x) - self:-j * getI(x));
end proc,
return Quaternion(self:-real * x, self:-i * x, self:-j * x, self:-k * x);
end proc,
return Quaternion(self:-real * x, self:-i * x, self:-j * x, self:-k * x);
end
]);

# redirect division to . operator
export *::static := overload([
use * = . in return self * x; end use
end proc,
use * = . in return x * self; end use
end proc,
use * = . in return x * self; end use
end
]);

# convert quaternion to multiplicative inverse
export /::static := overload([
return Conjugate(self) . (1/(Norm(self)^2));
end proc
]);

# QuaternionCommutator computes the commutator of self and x
export QuaternionCommutator::static := proc(x::Quaternion, y::Quaternion, $) return (x . y) - (y . x); end proc; # display quaternion export ModulePrint::static := proc(self::Quaternion,$);
return cat(self:-real, " + ", self:-i, "i + ", self:-j, "j + ", self:-k, "k"):
end proc;

export ModuleApply::static := proc()
Object(Quaternion, _passed);
end proc;

export ModuleCopy::static := proc(new::Quaternion, proto::Quaternion, R::algebraic, imag::algebraic, J::algebraic, K::algebraic, $) new:-real := R; new:-i := imag; new:-j := J; new:-k := K; end proc; end module: q := Quaternion(1, 2, 3, 4): q1 := Quaternion(2, 3, 4, 5): q2 := Quaternion(3, 4, 5, 6): r := 7: quats := Array([q, q1, q2]): print("q, q1, q2"): seq(quats[i], i = 1..3); print("norms"): seq(Norm(quats[i]), i = 1..3); print("negative"): seq(NegativeQuaternion(quats[i]), i = 1..3); print("conjugate"): seq(Conjugate(quats[i]), i = 1..3); print("addition of real number 7"): seq(quats[i] + r, i = 1..3); print("multiplication by real number 7"): seq(quats[i] . r, i = 1..3); print("division by real number 7"): seq(quats[i] / 7, i = 1..3); print("add quaternions q1 and q2"): q1 + q2; print("multiply quaternions q1 and q2"); q1 . q2; print("multiply quaternions q2 and q1"): q2 . q1; print("quaternion commutator of q1 and q2"): QuaternionCommutator(q1,q2); print("divide q1 by q2"): q1 / q2; Output:  "q, q1, q2" 1 + 2i + 3j + 4k, 2 + 3i + 4j + 5k, 3 + 4i + 5j + 6k "norms" 1/2 1/2 1/2 30 , 3 6 , 86 "negative" -1 + -2i + -3j + -4k, -2 + -3i + -4j + -5k, -3 + -4i + -5j + -6k "conjugate" 1 + -2i + -3j + -4k, 2 + -3i + -4j + -5k, 3 + -4i + -5j + -6k "addition of real number 7" 8 + 2i + 3j + 4k, 9 + 3i + 4j + 5k, 10 + 4i + 5j + 6k "multiplication by real number 7" 7 + 14i + 21j + 28k, 14 + 21i + 28j + 35k, 21 + 28i + 35j + 42k "division by real number 7" 1/7 + 2/7i + 3/7j + 4/7k, 2/7 + 3/7i + 4/7j + 5/7k, 3/7 + 4/7i + 5/7j + 6/7k "add quaternions q1 and q2" 5 + 7i + 9j + 11k "multiply quaternions q1 and q2" -56 + 16i + 24j + 26k "multiply quaternions q2 and q1" -56 + 18i + 20j + 28k "quaternion commutator of q1 and q2" 0 + -2i + 4j + -2k "divide q1 by q2" 34/43 + 1/43i + 0j + 2/43k  ## Mathematica /Wolfram Language <<Quaternions q=Quaternion[1,2,3,4] q1=Quaternion[2,3,4,5] q2=Quaternion[3,4,5,6] r=7 ->Quaternion[1,2,3,4] ->Quaternion[2,3,4,5] ->Quaternion[3,4,5,6] ->7 Abs[q] ->√30 -q ->Quaternion[-1,-2,-3,-4] Conjugate[q] ->Quaternion[1,-2,-3,-4] r+q ->Quaternion[8,2,3,4] q+r ->Quaternion[8,2,3,4] q1+q2 ->Quaternion[5,7,9,11] q*r ->Quaternion[7,14,21,28] r*q ->Quaternion[7,14,21,28] q1**q2 ->Quaternion[-56,16,24,26] q2**q1 ->Quaternion[-56,18,20,28]  ## Mercury A possible implementation of quaternions in Mercury (the simplest representation) would look like this. Note that this is a full module implementation, complete with boilerplate, and that it works by giving an explicit conversion function for floats, converting a float into a quaternion representation of that float. Thus the float value 7.0 gets turned into the quaternion representation q(7.0, 0.0, 0.0, 0.0) through the function call r(7.0). :- module quaternion. :- interface. :- import_module float. :- type quaternion ---> q( w :: float, i :: float, j :: float, k :: float ). % conversion :- func r(float) = quaternion is det. % operations :- func norm(quaternion) = float is det. :- func -quaternion = quaternion is det. :- func conjugate(quaternion) = quaternion is det. :- func quaternion + quaternion = quaternion is det. :- func quaternion * quaternion = quaternion is det. :- implementation. :- import_module math. % conversion r(W) = q(W, 0.0, 0.0, 0.0). % operations norm(q(W, I, J, K)) = math.sqrt(W*W + I*I + J*J + K*K). -q(W, I, J, K) = q(-W, -I, -J, -K). conjugate(q(W, I, J, K)) = q(W, -I, -J, -K). q(W0, I0, J0, K0) + q(W1, I1, J1, K1) = q(W0+W1, I0+I1, J0+J1, K0+K1). q(W0, I0, J0, K0) * q(W1, I1, J1, K1) = q(W0*W1 - I0*I1 - J0*J1 - K0*K1, W0*I1 + I0*W1 + J0*K1 - K0*J1, W0*J1 - I0*K1 + J0*W1 + K0*I1, W0*K1 + I0*J1 - J0*I1 + K0*W1 ). The following test module puts the module through its paces. :- module test_quaternion. :- interface. :- import_module io. :- pred main(io::di, io::uo) is det. :- implementation. :- import_module quaternion. :- import_module exception. :- import_module float. :- import_module list. :- import_module string. :- func to_string(quaternion) = string is det. main(!IO) :- Q = q(1.0, 2.0, 3.0, 4.0), Q1 = q(2.0, 3.0, 4.0, 5.0), Q2 = q(3.0, 4.0, 5.0, 6.0), R = 7.0, QR = r(R), io.print("Q = ", !IO), io.print(to_string(Q), !IO), io.nl(!IO), io.print("Q1 = ", !IO), io.print(to_string(Q1), !IO), io.nl(!IO), io.print("Q2 = ", !IO), io.print(to_string(Q2), !IO), io.nl(!IO), io.print("R = ", !IO), io.print(R, !IO), io.nl(!IO), io.nl(!IO), io.print("1. The norm of a quaternion.\n", !IO), io.print("norm(Q) = ", !IO), io.print(norm(Q), !IO), io.nl(!IO), io.nl(!IO), io.print("2. The negative of a quaternion.\n", !IO), io.print("-Q = ", !IO), io.print(to_string(-Q), !IO), io.nl(!IO), io.nl(!IO), io.print("3. The conjugate of a quaternion.\n", !IO), io.print("conjugate(Q) = ", !IO), io.print(to_string(conjugate(Q)), !IO), io.nl(!IO), io.nl(!IO), io.print("4. Addition of a real number and a quaternion.\n", !IO), ( Q + QR = QR + Q -> io.print("Addition is commutative.\n", !IO) ; io.print("Addition is not commutative.\n", !IO) ), io.print("Q + R = ", !IO), io.print(to_string(Q + QR), !IO), io.nl(!IO), io.print("R + Q = ", !IO), io.print(to_string(QR + Q), !IO), io.nl(!IO), io.nl(!IO), io.print("5. Addition of two quaternions.\n", !IO), ( Q1 + Q2 = Q2 + Q1 -> io.print("Addition is commutative.\n", !IO) ; io.print("Addition is not commutative.\n", !IO) ), io.print("Q1 + Q2 = ", !IO), io.print(to_string(Q1 + Q2), !IO), io.nl(!IO), io.print("Q2 + Q1 = ", !IO), io.print(to_string(Q2 + Q1), !IO), io.nl(!IO), io.nl(!IO), io.print("6. Multiplication of a real number and a quaternion.\n", !IO), ( Q * QR = QR * Q -> io.print("Multiplication is commutative.\n", !IO) ; io.print("Multiplication is not commutative.\n", !IO) ), io.print("Q * R = ", !IO), io.print(to_string(Q * QR), !IO), io.nl(!IO), io.print("R * Q = ", !IO), io.print(to_string(QR * Q), !IO), io.nl(!IO), io.nl(!IO), io.print("7. Multiplication of two quaternions.\n", !IO), ( Q1 * Q2 = Q2 * Q1 -> io.print("Multiplication is commutative.\n", !IO) ; io.print("Multiplication is not commutative.\n", !IO) ), io.print("Q1 * Q2 = ", !IO), io.print(to_string(Q1 * Q2), !IO), io.nl(!IO), io.print("Q2 * Q1 = ", !IO), io.print(to_string(Q2 * Q1), !IO), io.nl(!IO), io.nl(!IO). to_string(q(I, J, K, W)) = string.format("q(%f, %f, %f, %f)", [f(I), f(J), f(K), f(W)]). :- end_module test_quaternion. The output of the above code follows: % ./test_quaternion Q = q(1.000000, 2.000000, 3.000000, 4.000000) Q1 = q(2.000000, 3.000000, 4.000000, 5.000000) Q2 = q(3.000000, 4.000000, 5.000000, 6.000000) R = 7.0 1. The norm of a quaternion. norm(Q) = 5.477225575051661 2. The negative of a quaternion. -Q = q(-1.000000, -2.000000, -3.000000, -4.000000) 3. The conjugate of a quaternion. conjugate(Q) = q(1.000000, -2.000000, -3.000000, -4.000000) 4. Addition of a real number and a quaternion. Addition is commutative. Q + R = q(8.000000, 2.000000, 3.000000, 4.000000) R + Q = q(8.000000, 2.000000, 3.000000, 4.000000) 5. Addition of two quaternions. Addition is commutative. Q1 + Q2 = q(5.000000, 7.000000, 9.000000, 11.000000) Q2 + Q1 = q(5.000000, 7.000000, 9.000000, 11.000000) 6. Multiplication of a real number and a quaternion. Multiplication is commutative. Q * R = q(7.000000, 14.000000, 21.000000, 28.000000) R * Q = q(7.000000, 14.000000, 21.000000, 28.000000) 7. Multiplication of two quaternions. Multiplication is not commutative. Q1 * Q2 = q(-56.000000, 16.000000, 24.000000, 26.000000) Q2 * Q1 = q(-56.000000, 18.000000, 20.000000, 28.000000)  ## Nim For simplicity, we have limited the type of quaternion fields to floats (i.e. float64). An implementation could use a generic type in order to allow other field types such as float32. import math, tables type Quaternion* = object a, b, c, d: float func initQuaternion*(a, b, c, d = 0.0): Quaternion = Quaternion(a: a, b: b, c: c, d: d) func -*(q: Quaternion): Quaternion = initQuaternion(-q.a, -q.b, -q.c, -q.d) func +*(q: Quaternion; r: float): Quaternion = initQuaternion(q.a + r, q.b, q.c, q.d) func +*(r: float; q: Quaternion): Quaternion = initQuaternion(q.a + r, q.b, q.c, q.d) func +*(q1, q2: Quaternion): Quaternion = initQuaternion(q1.a + q2.a, q1.b + q2.b, q1.c + q2.c, q1.d + q2.d) func **(q: Quaternion; r: float): Quaternion = initQuaternion(q.a * r, q.b * r, q.c * r, q.d * r) func **(r: float; q: Quaternion): Quaternion = initQuaternion(q.a * r, q.b * r, q.c * r, q.d * r) func **(q1, q2: Quaternion): Quaternion = initQuaternion(q1.a * q2.a - q1.b * q2.b - q1.c * q2.c - q1.d * q2.d, q1.a * q2.b + q1.b * q2.a + q1.c * q2.d - q1.d * q2.c, q1.a * q2.c - q1.b * q2.d + q1.c * q2.a + q1.d * q2.b, q1.a * q2.d + q1.b * q2.c - q1.c * q2.b + q1.d * q2.a) func conjugate*(q: Quaternion): Quaternion = initQuaternion(q.a, -q.b, -q.c, -q.d) func norm*(q: Quaternion): float = sqrt(q.a * q.a + q.b * q.b + q.c * q.c + q.d * q.d) func ==*(q: Quaternion; r: float): bool = if q.b != 0 or q.c != 0 or q.d != 0: false else: q.a == r func $(q: Quaternion): string =
## Return the representation of a quaternion.
const Letter = {"a": "", "b": "i", "c": "j", "d": "k"}.toTable
if q == 0: return "0"
for name, value in q.fieldPairs:
if value != 0:
var val = value
if result.len != 0:
result.add if value >= 0: '+' else: '-'
val = abs(val)
result.add $val & Letter[name] when isMainModule: let q = initQuaternion(1, 2, 3, 4) q1 = initQuaternion(2, 3, 4, 5) q2 = initQuaternion(3, 4, 5, 6) r = 7.0 echo "∥q∥ = ", norm(q) echo "-q = ", -q echo "q* = ", conjugate(q) echo "q + r = ", q + r echo "r + q = ", r + q echo "q1 + q2 = ", q1 + q2 echo "qr = ", q * r echo "rq = ", r * q echo "q1 * q2 = ", q1 * q2 echo "q2 * q1 = ", q2 * q1  Output: ∥q∥ = 5.477225575051661 -q = -1.0-2.0i-3.0j-4.0k q* = 1.0-2.0i-3.0j-4.0k q + r = 8.0+2.0i+3.0j+4.0k r + q = 8.0+2.0i+3.0j+4.0k q1 + q2 = 5.0+7.0i+9.0j+11.0k qr = 7.0+14.0i+21.0j+28.0k rq = 7.0+14.0i+21.0j+28.0k q1 * q2 = -56.0+16.0i+24.0j+26.0k q2 * q1 = -56.0+18.0i+20.0j+28.0k As can be seen, q1 * q2 != q2 * q1. ## OCaml This implementation was build strictly to the specs without looking (too much) at other implementations. The implementation as a record type with only floats is said (on the ocaml mailing list) to be especially efficient. Put this into a file quaternion.ml: type quaternion = {a: float; b: float; c: float; d: float} let norm q = sqrt (q.a**2.0 +. q.b**2.0 +. q.c**2.0 +. q.d**2.0 ) let floatneg r = ~-. r (* readability *) let negative q = {a = floatneg q.a; b = floatneg q.b; c = floatneg q.c; d = floatneg q.d } let conjugate q = {a = q.a; b = floatneg q.b; c = floatneg q.c; d = floatneg q.d } let addrq r q = {q with a = q.a +. r} let addq q1 q2 = {a = q1.a +. q2.a; b = q1.b +. q2.b; c = q1.c +. q2.c; d = q1.d +. q2.d } let multrq r q = {a = q.a *. r; b = q.b *. r; c = q.c *. r; d = q.d *. r } let multq q1 q2 = {a = q1.a*.q2.a -. q1.b*.q2.b -. q1.c*.q2.c -. q1.d*.q2.d; b = q1.a*.q2.b +. q1.b*.q2.a +. q1.c*.q2.d -. q1.d*.q2.c; c = q1.a*.q2.c -. q1.b*.q2.d +. q1.c*.q2.a +. q1.d*.q2.b; d = q1.a*.q2.d +. q1.b*.q2.c -. q1.c*.q2.b +. q1.d*.q2.a } let qmake a b c d = {a;b;c;d} (* readability omitting a= b=... *) let qstring q = Printf.sprintf "(%g, %g, %g, %g)" q.a q.b q.c q.d ;; (* test data *) let q = qmake 1.0 2.0 3.0 4.0 let q1 = qmake 2.0 3.0 4.0 5.0 let q2 = qmake 3.0 4.0 5.0 6.0 let r = 7.0 let () = (* written strictly to spec *) let pf = Printf.printf in pf "starting with data q=%s, q1=%s, q2=%s, r=%g\n" (qstring q) (qstring q1) (qstring q2) r; pf "1. norm of q = %g \n" (norm q) ; pf "2. negative of q = %s \n" (qstring (negative q)); pf "3. conjugate of q = %s \n" (qstring (conjugate q)); pf "4. adding r to q = %s \n" (qstring (addrq r q)); pf "5. adding q1 and q2 = %s \n" (qstring (addq q1 q2)); pf "6. multiply r and q = %s \n" (qstring (multrq r q)); pf "7. multiply q1 and q2 = %s \n" (qstring (multq q1 q2)); pf "8. instead q2 * q1 = %s \n" (qstring (multq q2 q1)); pf "\n";  using this file on the command line will produce: $ ocaml quaternion.ml
starting with data q=(1, 2, 3, 4), q1=(2, 3, 4, 5),  q2=(3, 4, 5, 6), r=7
1. norm of      q     = 5.47723
2. negative of  q     = (-1, -2, -3, -4)
3. conjugate of q     = (1, -2, -3, -4)
4. adding r to q      = (8, 2, 3, 4)
5. adding q1 and q2   = (5, 7, 9, 11)
6. multiply r and q   = (7, 14, 21, 28)
7. multiply q1 and q2 = (-56, 16, 24, 26)
8. instead q2 * q1    = (-56, 18, 20, 28)


For completeness, and since data types are of utmost importance in OCaml, here the types produced by pasting the code into the toplevel (ocaml is the toplevel):

type quaternion = { a : float; b : float; c : float; d : float; }
val norm : quaternion -> float = <fun>
val floatneg : float -> float = <fun>
val negative : quaternion -> quaternion = <fun>
val conjugate : quaternion -> quaternion = <fun>
val addrq : float -> quaternion -> quaternion = <fun>
val addq : quaternion -> quaternion -> quaternion = <fun>
val multrq : float -> quaternion -> quaternion = <fun>
val multq : quaternion -> quaternion -> quaternion = <fun>
val qmake : float -> float -> float -> float -> quaternion = <fun>
val qstring : quaternion -> string = <fun>


## Octave

There is an add-on package (toolbox) to Octave available from http://octave.sourceforge.net/quaternion/

Such a package can be install with the command:

pkg install -forge quaternion


Here is a sample interactive session solving the task:

> q = quaternion (1, 2, 3, 4)
q = 1 + 2i + 3j + 4k
>  q1 = quaternion (2, 3, 4, 5)
q1 = 2 + 3i + 4j + 5k
> q2 = quaternion (3, 4, 5, 6)
q2 = 3 + 4i + 5j + 6k
> r = 7
r =  7
> norm(q)
ans =  5.4772
> -q
ans = -1 - 2i - 3j - 4k
> conj(q)
ans = 1 - 2i - 3j - 4k
> q + r
ans = 8 + 2i + 3j + 4k
> q1 + q2
ans = 5 + 7i + 9j + 11k
> q * r
ans = 7 + 14i + 21j + 28k
> q1 * q2
ans = -56 + 16i + 24j + 26k
> q1 == q2
ans = 0


## Oforth

Setting a priority (here 160) to Quaternion class and defining #asQuaternion, integers and floats can be fully mixed with quaternions. neg is defined as "0 self -" into Number class, so no need to define it (if #- is defined).

160 Number Class newPriority: Quaternion(a, b, c, d)

Quaternion method: _a  @a ;
Quaternion method: _b  @b ;
Quaternion method: _c  @c ;
Quaternion method: _d  @d ;

Quaternion method: initialize  := d := c := b := a ;
Quaternion method: <<  '(' <<c @a << ',' <<c @b << ',' <<c @c << ',' <<c @d << ')' <<c ;

Integer method: asQuaternion  self 0 0 0 Quaternion new ;
Float   method: asQuaternion  self 0 0 0 Quaternion new ;

Quaternion method: ==(q)  q _a @a == q _b @b == and q _c @c == and q _d @d == and ;
Quaternion method: norm   @a sq @b sq + @c sq + @d sq + sqrt ;
Quaternion method: conj   @a  @b neg  @c neg  @d neg Quaternion new ;
Quaternion method: +(q)   Quaternion new(q _a @a +, q _b @b +, q _c @c +, q _d @d +) ;
Quaternion method: -(q)   Quaternion new(q _a @a -, q _b @b -, q _c @c -, q _d @d -) ;

Quaternion method: *(q)
Quaternion new(q _a @a * q _b @b * - q _c @c * - q _d @d * -,
q _a @b * q _b @a * + q _c @d * + q _d @c * -,
q _a @c * q _b @d * - q _c @a * + q _d @b * +,
q _a @d * q _b @c * + q _c @b * - q _d @a * + ) ;

Usage :

: test
| q q1 q2 r |

Quaternion new(1, 2, 3, 4) ->q
Quaternion new(2, 3, 4, 5) ->q1
Quaternion new(3, 4, 5, 6) ->q2
7.0 -> r

System.Out "q       = " << q << cr
System.Out "q1      = " << q1 << cr
System.Out "q2      = " << q2 << cr

System.Out "norm q  = " << q norm << cr
System.Out "neg q   = " << q neg << cr
System.Out "conj q  = " << q conj << cr
System.Out "q +r    = " << q r + << cr
System.Out "q1 + q2 = " << q1 q2 + << cr
System.Out "q * r   = " << q r * << cr
System.Out "q1 * q2 = " << q1 q2 * << cr
q1 q2 * q2 q1 * == ifFalse: [ "q1q2 and q2q1 are different quaternions" println ] ;
Output:
q       = (1,2,3,4)
q1      = (2,3,4,5)
q2      = (3,4,5,6)
norm q  = 5.47722557505166
neg q   = (-1,-2,-3,-4)
conj q  = (1,-2,-3,-4)
q +r    = (8,2,3,4)
q1 + q2 = (5,7,9,11)
q * r   = (7,14,21,28)
q1 * q2 = (-56,16,24,26)
q1q2 and q2q1 are different quaternions


## Ol

;;
;; This program is written to run without modification both in Otus
;; Lisp and in any of many Scheme dialects. I assume the presence of
;; "case-lambda", but not of "let-values". The program has worked
;; (without modification) in Otus Lisp 2.4, Guile >= 2.0 (but not in
;; Guile version 1.8), CHICKEN Scheme 5.3.0, Chez Scheme 9.5.8, Gauche
;; Scheme 0.9.12, Ypsilon 0.9.6-update3.
;;
;; Here a quaternion is represented as a linked list of four real
;; numbers. Such a representation probably has the greatest
;; portability between Scheme dialects. However, this representation
;; can be replaced, simply by redefining the procedures "quaternion?",
;; "quaternion-components", "quaternion->list", and "quaternion".
;;

(define (quaternion? q)               ; Can q be used as a quaternion?
(and (pair? q)
(let ((a (car q))
(q (cdr q)))
(and (real? a) (pair? q)
(let ((b (car q))
(q (cdr q)))
(and (real? b) (pair? q)
(let ((c (car q))
(q (cdr q)))
(and (real? c) (pair? q)
(let ((d (car q))
(q (cdr q)))
(and (real? d) (null? q)))))))))))

(define (quaternion-components q)       ; Extract the basis components.
(let ((a (car q))
(q (cdr q)))
(let ((b (car q))
(q (cdr q)))
(let ((c (car q))
(q (cdr q)))
(let ((d (car q)))
(values a b c d))))))

(define (quaternion->list q)     ; Get a list of the basis components.
q)

(define quaternion                      ; Make a quaternion.
(case-lambda
((a b c d)
;; Make the quaternion from basis components.
(list a b c d))
((q)
;; Make the quaternion from a scalar or from another quaternion.
;; WARNING: in the latter case, the quaternion is NOT
;; copied. This is not a problem, if you avoid things like
;; "set-car!" and "set-cdr!".
(if (real? q)
(list q 0 0 0)
q))))

(define (quaternion-norm q)      ; The euclidean norm of a quaternion.
(let ((q (quaternion q)))
(call-with-values (lambda () (quaternion-components q))
(lambda (a b c d)
(sqrt (+ (* a a) (* b b) (* c c) (* d d)))))))

(define (quaternion-conjugate q)        ; Conjugate a quaternion.
(let ((q (quaternion q)))
(call-with-values (lambda () (quaternion-components q))
(lambda (a b c d)
(quaternion a (- b) (- c) (- d))))))

(lambda (q1 q2)
(let ((q1 (quaternion q1))
(q2 (quaternion q2)))
(call-with-values
(lambda () (quaternion-components q1))
(lambda (a1 b1 c1 d1)
(call-with-values
(lambda () (quaternion-components q2))
(lambda (a2 b2 c2 d2)
(quaternion (+ a1 a2) (+ b1 b2)
(+ c1 c2) (+ d1 d2))))))))))
(case-lambda
(() (quaternion 0))
((q . q*)
(let loop ((accum q)
(q* q*))
(if (pair? q*)
(loop (quaternion-add accum (car q*)) (cdr q*))
accum))))))

(define`