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Arithmetic evaluation: Difference between revisions

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Arithmetic evaluation (view source)

Revision as of 03:52, 24 December 2012

7,283 bytes removed ,  11 years ago
m
→‎{{header|REXX}}: reworked the REXX program. -- ~~~~ !
m (→‎{{header|REXX}}: Deleted a comment from the REXX section header. -- ~~~~)
m (→‎{{header|REXX}}: reworked the REXX program. -- ~~~~ !)
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* 12.3D+44     ("double" precision)
* 12.3Q+44     ("extended" or "quad" precision)
<lang rexx></lang>
<lang rexx>/*REXX pgm evaluates an infix-type arithmetic expression & shows result.*/
nchars = '0123456789.eEdDqQ' /*possible parts of a #, sans ± */
e='***error!***'; $=' '; doubleOps='&|*/'; z=
parse arg x 1 ox1; if x='' then call serr 'no input was specified.'
x=space(x); L=length(x)
 
j=0; do forever; j=j+1; if j>L then leave; _=substr(x,j,1); _2=getX()
newT=pos(_,' ()[]{}^÷')\==0; if newT then do; z=z _ $; iterate; end
possDouble=pos(_,doubleOps)\==0 /*is _ a possible double operator*/
if possDouble then do /*is this a possible double oper?*/
if _2==_ then do /*yup, it's one of 'em.*/
_=_||_ /*use a double operator*/
x=overlay($,x,Nj) /*blank out the*/
end /* 2nd symbol.*/
z=z _ $; iterate
end
if _=='+' | _=="-" then do; p_=word(z,words(z)) /*last Z token*/
if p_=='(' then z=z 0 /handle unary ±*/
z=z _ $; iterate
end
lets=0; sigs=0; #=_
 
do j=j+1 to L; _=substr(x,j,1) /*build a valid number.*/
if lets==1 & sigs==0 then if _=='+' | _=='-' then do; sigs=1
#=# || _
iterate
end /*exp*/
if pos(_,nchars)==0 then leave
lets=lets+datatype(_,'M') /*keep track of # of exponents. */
#=# || translate(_,'EEEEE','eDdQq') /*keep buildingthe num.*/
end /*j*/
j=j-1
if \datatype(#,'N') then call serr 'invalid number: ' #
z=z # $
end /*forever*/
 
_=word(z,1); if _=='+' | _=='-' then z=0 z /*handle unary cases.*/
z=translate(z,'()()',"[]{}") /*support more grouping symbols. */
x='(' space(z) ') '; tokens=words(x) /*force stacking for expression. */
do i=1 for tokens; @.i=word(x,i); end /*i*/ /*assign input tokens*/
L=max(20,length(x)) /*use 20 for the min show width. */
op=')(-+/*^'; rOp=substr(op,3); p.=; s.=; n=length(op); RPN=; stack=
 
do i=1 for n; _=substr(op,i,1); s._=(i+1)%2; p._=s._+(i==n); end /*i*/
/*[↑] assign operator priorities.*/
do #=1 for tokens; ?=@.# /*process each token from @. list*/
if ?=='**' then ?="^" /*convert REXX-type exponentation*/
select /*@.# is: (, operator, ), operand*/
when ?=='(' then stack='(' stack
when isOp(?) then do /*is token an operator?*/
!=word(stack,1) /*get token from stack.*/
do while !\==')' & s.!>=p.?; RPN=RPN ! /*add*/
stack=subword(stack,2); /*del token from stack.*/
!=word(stack,1) /*get token from stack.*/
end /*while ···)*/
stack=? stack /*add token to stack.*/
end
when ?==')' then do; !=word(stack,1) /*get token from stack.*/
do while !\=='('; RPN=RPN ! /*add to RPN.*/
stack=subword(stack,2) /*del token from stack.*/
!=word(stack,1) /*get token from stack.*/
end /*while ···( */
stack=subword(stack,2) /*del token from stack.*/
end
otherwise RPN=RPN ? /*add operand to RPN. */
end /*select*/
end /*#*/
 
RPN=space(RPN stack); tokens=words(RPN); x=RPN; z=; stack=
do i=1 for tokens; @.i=word(RPN,i); end /*i*/ /*assign input tokens*/
dop='/ // % ÷'; bop='& | &&' /*division ops; binary operands*/
aop='- + * ^ **' dop bop; lop=aop '||' /*arithmetic ops; legal operands*/
 
do #=1 for tokens; ?=@.#; ??=? /*process each token from @. list*/
w=words(stack); b=word(stack,max(1,w)) /*stack count; last entry.*/
a=word(stack,max(1,w-1)) /*stack's "first" operand.*/
division =wordpos(?,dop)\==0 /*flag: doing a division.*/
arith =wordpos(?,aop)\==0 /*flag: doing arithmetic.*/
bitOp =wordpos(?,bop)\==0 /*flag: doing binary math*/
if datatype(?,'N') then do; stack=stack ?; iterate; end
if wordpos(?,lop)==0 then do; z=e 'illegal operator:' ?; leave; end
if w<2 then do; z=e 'illegal RPN expression.'; leave; end
if ?=='^' then ??="**" /*REXXify ^ ──► ** (make legal)*/
if ?=='÷' then ??="/" /*REXXify ÷ ──► / (make legal)*/
if division & b=0 then do; z=e 'division by zero: ' b; leave; end
if bitOp & \isBit(a) then do; z=e "token isn't logical: " a; leave; end
if bitOp & \isBit(b) then do; z=e "token isn't logical: " b; leave; end
select /*perform arith. operation*/
when ??=='+' then y = a + b
when ??=='-' then y = a - b
when ??=='*' then y = a * b
when ??=='/' | ??=="÷" then y = a / b
when ??=='//' then y = a // b
when ??=='%' then y = a % b
when ??=='^' | ??=="**" then y = a ** b
when ??=='||' then y = a || b
otherwise z=e 'invalid operator:' ?; leave
end /*select*/
if datatype(y,'W') then y=y/1 /*normalize number with ÷ by 1.*/
_=subword(stack,1,w-2); stack=_ y /*rebuild the stack with answer. */
end /*#*/
 
if word(z,1)==e then stack= /*handle special case of errors. */
z=space(z stack) /*append any residual entries. */
say 'answer──►' z /*display the answer (result). */
parse source upper . how . /*invoked via C.L. or REXX pgm?*/
if how=='COMMAND' | ,
\datatype(z,'W') then exit /*stick a fork in it, we're done.*/
return z /*return Z ──► invoker (RESULT).*/
/*──────────────────────────────────subroutines─────────────────────────*/
isBit: return arg(1)==0 | arg(1)==1 /*returns 1 if arg1 is bin bit.*/
isOp: return pos(arg(1),rOp)\==0 /*is argument1 a "real" operator?*/
serr: say; say e arg(1); say; exit 13 /*issue an error message with txt*/
/*──────────────────────────────────GETX subroutine─────────────────────*/
getX: do Nj=j+1 to length(x); _n=substr(x,Nj,1); if _n==$ then iterate
if _n==$ then iterate; return substr(x,Nj,1) /*ignore blanks*/
end /*Nj*/
return $ /*reached end-of-tokens, return $*/</lang>
'''output''' when using the input of: <tt> + 1+2.0-003e-00*[4/6] </tt>
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