Return multiple values

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Task
Return multiple values
You are encouraged to solve this task according to the task description, using any language you may know.

Show how to return more than one value from a function.

Contents

[edit] ACL2

;; To return multiple values:
(defun multiple-values (a b)
(mv a b))
 
;; To extract the values:
(mv-let (x y)
(multiple-values 1 2)
(+ x y))

[edit] Ada

Ada functions can only return one type. That type could be an array or record holding multiple values, but the usual method for returning several values is using a procedure with 'out' parameters. By default, all parameters are 'in', but can also be 'out', 'in out' and 'access'. Writing to an 'out' parameter simply changes the value of the variable passed to the procedure.

 
with Ada.Text_IO; use Ada.Text_IO;
procedure MultiReturn is
procedure SumAndDiff (x, y : Integer; sum, diff : out Integer) is begin
sum := x + y;
diff := x - y;
end SumAndDiff;
inta : Integer := 5;
intb : Integer := 3;
thesum, thediff : Integer;
begin
SumAndDiff (inta, intb, thesum, thediff);
Put_Line ("Sum:" & Integer'Image (thesum));
Put_Line ("Diff:" & Integer'Image (thediff));
end MultiReturn;
 
Output:
Sum: 8
Diff: 2

[edit] ATS

Every function returns one value. The conventional way to return multiple values is to return a tuple.

fn addsub (x: int, y: int): (int, int) =
(x+y, x-y)
 
implement main () = let
val (sum, diff) = addsub (33, 12)
in
print! ("33 + 12 = ", sum, "\n");
print! ("33 - 12 = ", diff, "\n")
end

[edit] AutoHotkey

Works with: AutoHotkey_L

Functions may return one value. The conventional way to return multiple values is to bundle them into an Array.

addsub(x, y) {
return [x + y, x - y]
}

[edit] AutoIt

Return an array.

 
Func _AddSub($iX, $iY)
Local $aReturn[2]
$aReturn[0] = $iX + $iY
$aReturn[1] = $iX - $iY
Return $aReturn
EndFunc
 

[edit] BBC BASIC

The most straightforward way of returning multiple values is to specify them as RETURNed parameters.

      PROCsumdiff(5, 3, sum, diff)
PRINT "Sum is " ; sum
PRINT "Difference is " ; diff
END
 
DEF PROCsumdiff(a, b, RETURN c, RETURN d)
c = a + b
d = a - b
ENDPROC

[edit] Bracmat

Translation of: Haskell

Every function returns one value. The conventional way to return multiple values is to return a tuple.

(addsub=x y.!arg:(?x.?y)&(!x+!y.!x+-1*!y));

You can use pattern matching to extract the components:

( addsub$(33.12):(?sum.?difference)
& out$("33 + 12 = " !sum)
& out$("33 - 12 = " !difference)
);

Output:

33 + 12 =  45
33 - 12 =  21

[edit] C

C has structures which can hold multiple data elements of varying types.

#include<stdio.h>
 
typedef struct{
int integer;
float decimal;
char letter;
char string[100];
double bigDecimal;
}Composite;
 
Composite example()
{
Composite C = {1, 2.3, 'a', "Hello World", 45.678};
return C;
}
 
 
int main()
{
Composite C = example();
 
printf("Values from a function returning a structure : { %d, %f, %c, %s, %f}\n", C.integer, C.decimal, C.letter, C.string, C.bigDecimal);
 
return 0;
}

Output:

Values from a function returning a structure : { 1, 2.300000, a, Hello World, 45.678000}

C99 and above also allow structure literals to refer to the name, rather than position, of the element to be initialized:

#include <stdio.h>
 
typedef struct {
char *first, *last;
} Name;
 
Name whatsMyName() {
return (Name) {
.first = "James",
.last = "Bond",
};
}
 
int main() {
Name me = whatsMyName();
printf("The name's %s. %s %s.\n", me.last, me.first, me.last);
return 0;
}

Output:

The name's Bond. James Bond.

[edit] C++

The new 2011 C++ standard includes tuples, which allow a number of different values of even different types to be passed around.

#include <algorithm>
#include <iostream>
#include <tuple>
 
std::tuple<const int , const int> minmax ( const int * numbers , const int num ) {
const int *maximum = std::max_element ( numbers , numbers + num ) ;
const int *minimum = std::min_element ( numbers , numbers + num ) ;
return std::make_tuple( *maximum , *minimum ) ;
}
 
int main( ) {
const int numbers[ ] = { 17 , 88 , 9 , 33 , 4 , 987 , -10 , 2 } ;
int numbersize = sizeof( numbers ) / sizeof ( int ) ;
std::tuple<const int , const int> result = minmax( numbers , numbersize ) ;
std::cout << "The greatest number is " << std::get<0>( result )
<< " , the smallest " << std::get<1>( result ) << " !\n" ;
return 0 ;
}

Output:

The greatest number is 987 , the smallest -10 !

[edit] C#

using System;
using System.Collections.Generic;
using System.Linq;
 
namespace ReturnMultipleValues
{
internal class Program
{
static void Main()
{
var minMax = MinMaxNum(new[] {4, 51, 1, -3, 3, 6, 8, 26, 2, 4});
 
int min = minMax.Item1;
int max = minMax.Item2;
 
Console.WriteLine("Min: {0}\nMax: {1}", min, max);
}
 
static Tuple<int,int> MinMaxNum(IEnumerable<int> nums)
{
var sortedNums = nums.OrderBy(num => num).ToArray();
return new Tuple<int, int>(sortedNums.First(), sortedNums.Last());
}
}
}

Output

Min: -3
Max: 51

[edit] Clipper

Every function returns one value. The conventional way to return multiple values is to bundle them into an array.

Function Addsub( x, y )
Return { x+y, x-y }

[edit] Clojure

Multiple values can be returned by packaging them in a vector. At receiving side, these arguments can be obtained individually by using destructuring.

(defn quot-rem [m n] [(quot m n) (rem m n)])
 
; The following prints 3 2.
(let [[q r] (quot-rem 11 3)]
(println q)
(println r))

In complex cases, it would make more sense to return a map, which can be destructed in a similar manner.

(defn quot-rem [m n]
{:q (quot m n)
 :r (rem m n)})
 
; The following prints 3 2.
(let [{:keys [q r]} (quot-rem 11 3)]
(println q)
(println r))

[edit] CMake

# Returns the first and last characters of string.
function(firstlast string first last)
# f = first character.
string(SUBSTRING "${string}" 0 1 f)
 
# g = last character.
string(LENGTH "${string}" length)
math(EXPR index "${length} - 1")
string(SUBSTRING "${string}" ${index} 1 g)
 
# Return both characters.
set("${first}" "${f}" PARENT_SCOPE)
set("${last}" "${g}" PARENT_SCOPE)
endfunction(firstlast)
 
firstlast("Rosetta Code" begin end)
message(STATUS "begins with ${begin}, ends with ${end}")

[edit] Common Lisp

Besides the obvious method of passing around a list, Common Lisp also allows a function to return multiple values. When citing the return values, if no interest is shown for multiple values, only the first (the primary return value) is used. Multiple values are not a data structure such as a tuple, list or array. They are a true mechanism for returning multiple values.

Returning a single value is accomplished by evaluating an expression (which itself yields a single value) at the end of a body of forms.

(defun return-three ()
3)

The next possibility is that of returning no values at all. For this, the values function is used, with no arguments:

(defun return-nothing ()
(values))

To combine the values of multiple expressions into a multi-value return, values is used with arguments. The following is from an interactive CLISP session. CLISP's listener shows multiple values separated by a semicolon:

[1]> (defun add-sub (x y) (values-list (list (+ x y) (- x y))))
ADD-SUB
[2]> (add-sub 4 2) ; 6 (primary) and 2
6 ;
2
[3]> (add-sub 3 1) ; 4 (primary) and 2
4 ;
2
[4]> (+ (add-sub 4 2) (add-sub 3 1)) ; 6 + 4
10
[5]> (multiple-value-call #'+ (add-sub 4 2) (add-sub 3 1)) ; 6+2+4+2
14

What happens if something tries to use the value of a form which returned (values)? In this case the behavior defaults to taking the value nil:

(car (values)) ;; no error: same as (car nil)

What if the values function is applied to some expressions which also yield multiple values, or which do not yield any values? The answer is that only the primary value is taken from each expression, or the value nil for any expression which did not yield a value:

(values (values 1 2 3) (values) 'a)

yields three values:

-> 1; NIL; A

This also means that values can be used to reduce a multiple value to a single value:

;; return exactly one value, no matter how many expr returns,
;; nil if expr returns no values
(values expr)

Multiple values are extracted in several ways.

1. Binding to variables:

(multiple-value-bind (dividend remainder) (truncate 16 3)
;; in this scope dividend is 5; remainder is 1
)

2. Conversion to a list:

(multiple-value-list (truncate 16 3)) ;; yields (5 1)

3. Reification of multiple values as arguments to another function:

;; pass arguments 5 1 to +, resulting in 6:
(multiple-value-call #'+ (truncate 16 3))

4. Assignment to variables:

;; assign 5 to dividend, 1 to remainder:
(multiple-value-setq (dividend remainder) (truncate 16 1))

(values ...) syntax is treated as a multiple value place by setf and other operators, allowing the above to be expressed this way:

(setf (values dividend remainder) (truncate 16 1))

[edit] D

import std.stdio, std.typecons;
 
auto addSub(T)(T x, T y) {
return tuple(x + y, x - y);
}
 
void main() {
auto r = addSub(33, 12);
writefln("33 + 12 = %d\n33 - 12 = %d", r.tupleof);
}
Output:
33 + 12 = 45
33 - 12 = 21

[edit] Déjà Vu

function-returning-multiple-values:
10 20
 
!print !print function-returning-multiple-values
 
Output:
10
20

[edit] Delphi/Pascal

Delphi functions return a single value, but var parameters of a function or procedure can be modified and act as return values.

program ReturnMultipleValues;
 
{$APPTYPE CONSOLE}
 
procedure GetTwoValues(var aParam1, aParam2: Integer);
begin
aParam1 := 100;
aParam2 := 200;
end;
 
var
x, y: Integer;
begin
GetTwoValues(x, y);
Writeln(x);
Writeln(y);
end.

[edit] ECL

MyFunc(INTEGER i1,INTEGER i2) := FUNCTION
RetMod := MODULE
EXPORT INTEGER Add  := i1 + i2;
EXPORT INTEGER Prod := i1 * i2;
END;
RETURN RetMod;
END;
 
//Reference each return value separately:
MyFunc(3,4).Add;
MyFunc(3,4).Prod;
 

[edit] Erlang

% Implemented by Arjun Sunel
-module(return_multi).
-export([main/0]).
 
main() ->
K=multiply(3,4),
C =lists:nth(1,K),
D = lists:nth(2,K),
E = lists:nth(3,K),
io:format("~p~n",[C]),
io:format("~p~n",[D]),
io:format("~p~n",[E]).
 
multiply(A,B) ->
case {A,B} of
{A, B} ->[A*B, A+B, A-B]
end.
 
Output:
12
7
-1
ok

[edit] Euphoria

Any Euphoria object can be returned. A sequence of objects can be returned, made from multiple data types as in this example.

include std\console.e --only for any_key, to help make running this program easy on windows GUI
 
integer aWholeNumber = 1
atom aFloat = 1.999999
sequence aSequence = {3, 4}
sequence result = {} --empty initialized sequence
 
function addmultret(integer first, atom second, sequence third)--takes three kinds of input, adds them all into one element of the..
return (first + second + third[1]) + third[2] & (first * second * third[1]) * third[2] --..output sequence and multiplies them into..
end function --..the second element
 
result = addmultret(aWholeNumber, aFloat, aSequence) --call function, assign what it gets into result - {9.999999, 23.999988}
? result
any_key()
Output:
{9.999999,23.999988}
Press Any Key to continue...

[edit] F#

A function always returns exactly one value. To return multiple results, they are typically packed into a tuple:

let addSub x y = x + y, x - y
 
let sum, diff = addSub 33 12
printfn "33 + 12 = %d" sum
printfn "33 - 12 = %d" diff

Output parameters from .NET APIs are automatically converted to tuples by the compiler. It is also possible to use output parameters explicitely with the byref keyword, but this is rarely necessary.

[edit] Factor

With stack-oriented languages like Factor, a function returns multiple values by pushing them on the data stack. For example, this word */ pushes both x*y and x/y.

USING: io kernel math prettyprint ;
IN: script
 
: */ ( x y -- x*y x/y )
[ * ] [ / ] 2bi ;
 
15 3 */
 
[ "15 * 3 = " write . ]
[ "15 / 3 = " write . ] bi*

Its stack effect declares that */ always returns 2 values. To return a variable number of values, a word must bundle those values into a sequence (perhaps an array or vector). For example, factors (defined in math.primes.factors and demonstrated at Prime decomposition#Factor) returns a sequence of prime factors.

[edit] FALSE

[\$@$@*@@/]f: { in: a b, out: a*b a/b }
6 2f;! .` ,. { 3 12 }

[edit] Forth

It is natural to return multiple values on the parameter stack. Many built-in operators and functions do so as well (/mod, open-file, etc.).

: muldiv ( a b -- a*b a/b )
2dup / >r * r> ;

[edit] Fortran

Translation of: Haskell
module multiple_values
implicit none
type res
integer :: p, m
end type
 
contains
 
function addsub(x,y) result(r)
integer :: x, y
type(res) :: r
r%p = x+y
r%m = x-y
end function
end module
 
program main
use multiple_values
print *, addsub(33, 22)
end program
 

[edit] Go

Functions can return multiple values in Go:

func addsub(x, y int) (int, int) {
return x + y, x - y
}

Or equivalently using named return style:

func addsub(x, y int) (sum, difference int) {
sum = x + y
difference = x - y
return
}

When a function returns multiple values, you must assign to a comma-separated list of targets:

sum, difference := addsub(33, 12)
fmt.Printf("33 + 12 = %d\n", sum)
fmt.Printf("33 - 12 = %d\n", difference)

[edit] Groovy

In Groovy functions return one value. One way to return multiple ones is to use anonymous maps as a sort of tuple.

def addSub(x,y) {
[
sum: x+y,
difference: x-y
]
}

Result:

addSub(10,12) 
 
["sum":22, "difference":-2]

[edit] Harbour

Every function returns one value. The conventional way to return multiple values is to bundle them into an array.

Function Addsub( x, y )
Return { x+y, x-y }

[edit] Haskell

Every function returns one value. The conventional way to return multiple values is to return a tuple.

addsub x y =
(x + y, x - y)

You can use pattern matching to extract the components:

main = do
let sum, difference = addsub 33 12
putStrLn $ "33 + 12 = " ++ show sum
putStrLn $ "33 - 12 = " ++ show difference

[edit] Icon and Unicon

Icon and Unicon values range from simple atomic values like integers and strings to structures like lists, tables, sets, records. The contents of structures are heterogeneous and any of them could be used to return multiple values all at once. Additionally, generators are supported that return multiple results one at a time as needed.

The following examples return 1, 2, 3 in different ways:

procedure retList() # returns as ordered list
return [1,2,3]
end
 
procedure retSet() # returns as un-ordered list
insert(S := set(),3,1,2)
return S
end
 
procedure retLazy() # return as a generator
suspend 1|2|3
end
 
procedure retTable() # return as a table
T := table()
T["A"] := 1
T["B"] := 2
T["C"] := 3
return T
end
 
record retdata(a,b,c)
 
procedure retRecord() # return as a record, least general method
return retdata(1,2,3)
end

[edit] J

To return multiple values in J, you return an array which contains multiple values. Since the only data type in J is array, this is sort of like asking how to return only one value in another language.

   1 2+3 4
4 6

[edit] Java

Translation of: NetRexx
import java.util.List;
import java.util.ArrayList;
import java.util.Map;
import java.util.HashMap;
 
// =============================================================================
public class RReturnMultipleVals {
public static final String K_lipsum = "Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.";
public static final Long K_1024 = 1024L;
public static final String L = "L";
public static final String R = "R";
 
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
public static void main(String[] args) throws NumberFormatException{
Long nv_;
String sv_;
switch (args.length) {
case 0:
nv_ = K_1024;
sv_ = K_lipsum;
break;
case 1:
nv_ = Long.parseLong(args[0]);
sv_ = K_lipsum;
break;
case 2:
nv_ = Long.parseLong(args[0]);
sv_ = args[1];
break;
default:
nv_ = Long.parseLong(args[0]);
sv_ = args[1];
for (int ix = 2; ix < args.length; ++ix) {
sv_ = sv_ + " " + args[ix];
}
break;
}
 
RReturnMultipleVals lcl = new RReturnMultipleVals();
 
Pair<Long, String> rvp = lcl.getPairFromPair(nv_, sv_); // values returned in a bespoke object
System.out.println("Results extracted from a composite object:");
System.out.printf("%s, %s%n%n", rvp.getLeftVal(), rvp.getRightVal());
 
List<Object> rvl = lcl.getPairFromList(nv_, sv_); // values returned in a Java Collection object
System.out.println("Results extracted from a Java Colections \"List\" object:");
System.out.printf("%s, %s%n%n", rvl.get(0), rvl.get(1));
 
Map<String, Object> rvm = lcl.getPairFromMap(nv_, sv_); // values returned in a Java Collection object
System.out.println("Results extracted from a Java Colections \"Map\" object:");
System.out.printf("%s, %s%n%n", rvm.get(L), rvm.get(R));
}
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
// Return a bespoke object.
// Permits any number and type of value to be returned
public <T, U> Pair<T, U> getPairFromPair(T vl_, U vr_) {
return new Pair<T, U>(vl_, vr_);
}
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
// Exploit Java Collections classes to assemble a collection of results.
// This example uses java.util.List
public List<Object> getPairFromList(Object nv_, Object sv_) {
List<Object> rset = new ArrayList<Object>();
rset.add(nv_);
rset.add(sv_);
return rset;
}
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
// Exploit Java Collections classes to assemble a collection of results.
// This example uses java.util.Map
public Map<String, Object> getPairFromMap(Object nv_, Object sv_) {
Map<String, Object> rset = new HashMap<String, Object>();
rset.put(L, nv_);
rset.put(R, sv_);
return rset;
}
 
// ===========================================================================
private static class Pair<L, R> {
private L leftVal;
private R rightVal;
 
public Pair(L nv_, R sv_) {
setLeftVal(nv_);
setRightVal(sv_);
}
public void setLeftVal(L nv_) {
leftVal = nv_;
}
public L getLeftVal() {
return leftVal;
}
public void setRightVal(R sv_) {
rightVal = sv_;
}
public R getRightVal() {
return rightVal;
}
}
}

[edit] Julia

function addsub(x, y)
return x + y, x - y
end
julia> addsub(10,4)
(14,6)


[edit] Lasso

define multi_value() => {
return (:'hello word',date)
}
// shows that single method call will return multiple values
// the two values returned are assigned in order to the vars x and y
local(x,y) = multi_value
 
'x: '+#x
'\ry: '+#y
Output:
x: hello word
y: 2013-11-06 01:03:47

[edit] Liberty BASIC

Using a space-delimited string to hold the array. LB functions return only one numeric or string value, so the function returns a string from which can be separated the two desired values.

data$ ="5 6 7 22 9 3 4 8 7 6 3 -5 2 1 8 9"
 
a$ =minMax$( data$)
print " Minimum was "; word$( a$, 1, " "); " & maximum was "; word$( a$, 2, " ")
 
end
 
function minMax$( i$)
min = 1E6
max =-1E6
i =1
do
t$ =word$( i$, i, " ")
if t$ ="" then exit do
v =val( t$)
min =min( min, v)
max =max( max, v)
i =i +1
loop until 0
minMax$ =str$( min) +" " +str$( max)
end function
 Minimum was -5 & maximum was 22

[edit] Lua

function addsub( a, b )
return a+b, a-b
end
 
s, d = addsub( 7, 5 )
print( s, d )

[edit] Maple

> sumprod := ( a, b ) -> (a + b, a * b):
> sumprod( x, y );
x + y, x y
 
> sumprod( 2, 3 );
5, 6

The parentheses are needed here only because of the use of arrow ("->") notation to define the procedure. One could do, instead:

sumprod := proc( a, b ) a + b, a * b end:

[edit] Mathematica

addsub [x_,y_]:= List [x+y,x-y]
addsub[4,2]
Output
{6,2}

[edit] MATLAB / Octave

  function [a,b,c]=foo(d)
a = 1-d;
b = 2+d;
c = a+b;
end;
[x,y,z] = foo(5)

Output:

  > [x,y,z] = foo(5) 
x = -4
y = 7
z = 3

[edit] Maxima

f(a, b) := [a * b, a + b]$
 
[u, v]: f(5, 6);
[30, 11]

[edit] Mercury

Mercury is a logic language. Its unification semantics permit any number of output parameters (the closest equivalent to return values). The sample code provided here centres on the addsub/4 predicate. The mode statement identifies the first two parameters as input parameters and the last two as output parameters, thus, in effect, returning two results. In this case the first output parameter returns the sum of the two inputs and the second output returns the difference of the two inputs.

[edit] addsub.m

:- module addsub.
 
:- interface.
:- import_module io.
:- pred main(io::di, io::uo) is det.
 
:- implementation.
:- import_module int, list, string.
 
main(!IO) :-
command_line_arguments(Args, !IO),
filter_map(to_int, Args, CleanArgs),
(length(CleanArgs, 2) ->
X = det_index1(CleanArgs,1),
Y = det_index1(CleanArgs,2),
addsub(X, Y, S, D),
format("%d + %d = %d\n%d - %d = %d\n",
[i(X), i(Y), i(S), i(X), i(Y), i(D)], !IO)
 ;
write_string("Please pass two integers on the command line.\n", !IO)
).
 
:- pred addsub(int::in, int::in, int::out, int::out) is det.
addsub(X, Y, S, D) :-
S = X + Y,
D = X - Y.
 
:- end_module addsub.

[edit] Use and output

$ mmc addsub.m -E && ./addsub 100 999   
100 + 999 = 1099
100 - 999 = -899

[edit] Functions and tuples

Mercury is also a functional language, thus a function-based implementation is also possible. Functions in Mercury can only return a single value, but Mercury allows the use of arbitrary tuples containing multiple heterogenous ad-hoc values which is, for all practical purposes, the same thing. The above code can be modified so that the definition of addsub/4 is now instead this function addsub/2:

:- func addsub(int, int) = {int, int}.
addsub(X, Y) = { X + Y, X - Y }.

Instead, now, of a predicate with two input and two output parameters of type int, addsub is a function that takes two int parameters and returns a tuple containing two int values. The call to addsub/4 in the above code is now replaced by this:

        {S, D} = addsub(X, Y),

All other code remains exactly the same as does the use and output of it.

[edit] Functions and type constructors

It should be noted that tuples as a construct are generally frowned upon in Mercury, relying as they do on structural type equivalence instead of nominative. The preferred approach is either to have multiple explicit output parameters on predicates or to have an explicit named type that covers the multi-return needs. An example of this follows:

:- module addsub.
 
:- interface.
:- import_module io.
:- pred main(io::di, io::uo) is det.
 
:- implementation.
:- import_module int, list, string.
 
:- type my_result ---> twin(int, int).
 
main(!IO) :-
command_line_arguments(Args, !IO),
filter_map(to_int, Args, CleanArgs),
(length(CleanArgs, 2) ->
X = det_index1(CleanArgs,1),
Y = det_index1(CleanArgs,2),
twin(S, D) = addsub(X, Y),
format("%d + %d = %d\n%d - %d = %d\n",
[i(X), i(Y), i(S), i(X), i(Y), i(D)], !IO)
 ;
write_string("Please pass two integers on the command line.\n", !IO)
).
 
:- func addsub(int, int) = my_result.
addsub(X, Y) = twin(X + Y, X - Y).
 
:- end_module addsub.

Here the type my_result has been provided with a twin/2 constructor that accepts two int values. Use and output of the code is, again, exactly the same.

addsub/2 explicitly constructs a my_result value with the paired calculations and this is deconstructed in the call in the main predicate through unification. While the resulting code is slightly more verbose than the tuple-based version it is more strongly protected against type errors and is more explicit in its intent at the same time.

[edit] Nemerle

To return multiple values in Nemerle, package them into a tuple.

using System;
using System.Console;
using Nemerle.Assertions;
 
module MultReturn
{
MinMax[T] (ls : list[T]) : T * T
where T : IComparable
requires ls.Length > 0 otherwise throw ArgumentException("An empty list has no extreme values.")
{
def greaterOf(a, b) { if (a.CompareTo(b) > 0) a else b }
def lesserOf(a, b) { if (a.CompareTo(b) < 0) a else b }
 
(ls.FoldLeft(ls.Head, lesserOf), ls.FoldLeft(ls.Head, greaterOf)) // packing tuple
}
 
Main() : void
{
def nums = [1, 34, 12, -5, 4, 0];
def (min, max) = MinMax(nums); // unpacking tuple
WriteLine($"Min of nums = $min; max of nums = $max");
}
}

[edit] NetRexx

While a NetRexx method can only return a single "thing" to it's caller that "thing" can be an object which may contain a great deal of information. Typical return objects can be composite objects, Java Collection Class objects, NetRexx indexed strings etc.

Another common idiom inherited from REXX is the ability to collect the return data into a simple NetRexx string. Caller can then use the PARSE instruction to deconstruct the return value and assign the parts to separate variables.

/* NetRexx */
options replace format comments java crossref symbols nobinary
 
-- =============================================================================
class RReturnMultipleVals public
properties constant
L = 'L'
R = 'R'
K_lipsum = 'Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.'
K_1024 = 1024
 
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
method RReturnMultipleVals() public
return
 
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
method main(args = String[]) public static
arg = Rexx(args)
parse arg nv_ sv_ .
if \nv_.datatype('n') then nv_ = K_1024
if sv_ = '' then sv_ = K_lipsum
 
lcl = RReturnMultipleVals()
 
rvr = lcl.getPair(nv_, sv_) -- multiple values returned as a string. Use PARSE to extract values
parse rvr val1 val2
say 'Results extracted from a NetRexx string:'
say val1',' val2
say
 
rvr = lcl.getPairFromRexx(nv_, sv_) -- values returned in a NetRexx indexed string
say 'Results extracted from a NetRexx "indexed string":'
say rvr[L]',' rvr[R]
say
 
rvp = lcl.getPairFromPair(nv_, sv_) -- values returned in a bespoke object
say 'Results extracted from a composite object:'
say rvp.getLeftVal',' rvp.getRightVal
say
 
rvl = lcl.getPairFromList(nv_, sv_) -- values returned in a Java Collection "List" object
say 'Results extracted from a Java Colections "List" object:'
say rvl.get(0)',' rvl.get(1)
say
 
rvm = lcl.getPairFromMap(nv_, sv_) -- values returned in a Java Collection "Map" object
say 'Results extracted from a Java Colections "Map" object:'
say rvm.get(L)',' rvm.get(R)
say
 
return
 
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- returns the values in a NetRexx string.
-- Caller can the power of PARSE to extract the results
method getPair(nv_, sv_) public returns Rexx
return nv_ sv_
 
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- Return the values as members of a NetRexx indexed string
method getPairFromRexx(nv_, sv_) public returns Rexx
rval = ''
rval[L] = nv_
rval[R] = sv_
return rval
 
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- Return a bespoke object.
-- Permits any number and type of value to be returned
method getPairFromPair(nv_, sv_) public returns RReturnMultipleVals.Pair
rset = RReturnMultipleVals.Pair(nv_, sv_)
return rset
 
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- Exploit Java Collections classes to assemble a collection of results.
-- This example uses java.util.List
method getPairFromList(nv_, sv_) public returns java.util.List
rset = ArrayList()
rset.add(nv_)
rset.add(sv_)
return rset
 
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- This example uses java.util.Map
method getPairFromMap(nv_, sv_) public returns java.util.Map
rset = HashMap()
rset.put(L, nv_)
rset.put(R, sv_)
return rset
 
-- =============================================================================
class RReturnMultipleVals.Pair dependent
 
properties indirect
leftVal
rightVal
 
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
method Pair(nv_ = parent.K_1024, sv_ = parent.K_lipsum) public
setLeftVal(nv_)
setRightVal(sv_)
return
 

[edit] OCaml

Every function returns one value. The conventional way to return multiple values is to return a tuple.

let addsub x y =
x + y, x - y

(Note that parentheses are not necessary for a tuple literal in OCaml.)

You can use pattern matching to extract the components:

let sum, difference = addsub 33 12 in
Printf.printf "33 + 12 = %d\n" sum;
Printf.printf "33 - 12 = %d\n" difference

[edit] Space safety of tuples

The OCaml programmer should be aware that when multiple values are returned with a tuple, the finalisation does not handle each values independently, but handles the tuple as a whole. So all the values are only finalised when all the values are not reachable anymore.

There is also an explanation of this behaviour in the module Space_safe_tuple of the Jane Street's core library.

let pair a b =
let ra = Array.create 1 a
and rb = Array.create 1 b in
let f r = Printf.printf "> finalised: %d\n%!" r.(0) in
Gc.finalise f ra;
Gc.finalise f rb;
(ra, rb)
 
let () =
let a, b = pair 1 2 in
let c, d = pair 3 4 in
Gc.full_major (); (* garbage collection *)
Printf.printf "Used: %d\n%!" a.(0)

Here we see that b is not finalised even if it is not used after the garbage collection:

$ ocamlopt -w y -o pair.opt pair.ml
$ ./pair.opt 
> finalised: 4
> finalised: 3
Used: 1

The workaround is to explicitly access to each value with functions like fst and snd that return only one element of the tuple:

val fst : 'a * 'b -> 'a
val snd : 'a * 'b -> 'b
let pair a b =
let ra = Array.create 1 a
and rb = Array.create 1 b in
let f r = Printf.printf "> finalised: %d\n%!" r.(0) in
Gc.finalise f ra;
Gc.finalise f rb;
(ra, rb)
 
let () =
let ab = pair 1 2 in
let a = fst ab
and b = snd ab in
let c, d = pair 3 4 in
Gc.full_major (); (* garbage collection *)
Printf.printf "Used: %d\n%!" a.(0)

Now we see that b is finalised:

$ ocamlopt -w y -o pair2.opt pair2.ml
$ ./pair2.opt 
> finalised: 4
> finalised: 3
> finalised: 2
Used: 1

[edit] ooRexx

Functions and methods in ooRexx can only have a single return value, but that return value can be some sort of collection or other object that contains multiple values. For example, an array:

 
r = addsub(3, 4)
say r[1] r[2]
 
::routine addsub
use arg x, y
return .array~of(x + y, x - y)
 

Output:

7 -1


[edit] OxygenBasic

Demonstrated with vectors, using OOP and a pseudo-assign trick:

 
 
'============
class vector4
'============
 
float w,x,y,z
 
method values(float fw,fx,fy,fz)
this <= fw, fx, fy, fz
end method
 
method values(vector4 *v)
this <= v.w, v.x, v.y, v.z
end method
 
method values() as vector4
return this
end method
 
method ScaledValues(float fw,fx,fy,fz) as vector4
static vector4 v
v <= w*fw, x*fx, y*fy, z*fz
return v
end method
 
method ShowValues() as string
string cm=","
return w cm x cm y cm z
end method
 
end class
 
vector4 aa,bb
 
bb.values = 1,2,3,4
 
aa.values = bb.Values()
 
print aa.ShowValues() 'result 1,2,3,4
 
aa.values = bb.ScaledValues(100,100,-100,100)
 
print aa.ShowValues() 'result 100,200,-300,400
 
 

[edit] PARI/GP

The usual way to return multiple values is to put them in a vector:

foo(x)={
[x^2, x^3]
};

[edit] Perl

Functions may return lists of values:

sub foo {
my ($a, $b) = @_;
return $a + $b, $a * $b;
}

[edit] Perl 6

Each function officially returns one value, but by returning a Parcel you can transparently return a lazy list of arbitrary size.

sub foo($a,$b) {
$a + $b, $a * $b, $b xx $a
}
 
say foo 3, 7;
Output:
10 21 7 7 7

[edit] PHP

Every function returns one value. The conventional way to return multiple values is to bundle them into an array.

function addsub($x, $y) {
return array($x + $y, $x - $y);
}

You can use the list() construct to assign to multiple variables:

list($sum, $difference) = addsub(33, 12);
echo "33 + 12 = $sum\n";
echo "33 - 12 = $difference\n";

[edit] PicoLisp

A PicoLisp function returns a single value. For multiple return values, a cons pair or a list may be used.

(de addsub (X Y)
(list (+ X Y) (- X Y)) )

Test:

: (addsub 4 2)
-> (6 2)
: (addsub 3 1)
-> (4 2)
: (+ (car (addsub 4 2)) (car (addsub 3 1)))
-> 10
: (sum + (addsub 4 2) (addsub 3 1))
-> 14

[edit] Pike

Multiple values are returned through an array. An array can be assigned to separate variables.

array(int) addsub(int x, int y)
{
return ({ x+y, x-y });
}
 
[int z, int w] = addsub(5,4);

[edit] PL/I

Example 1 illustrates a function that returns an array:

   define structure 1 h,
2 a (10) float;
declare i fixed binary;
 
sub: procedure (a, b) returns (type(h));
declare (a, b) float;
declare p type (h);
do i = 1 to 10;
p.a(i) = i;
end;
return (p);
end sub;

Example 2 illustrates a function that returns a general data structure:

   define structure 1 customer,
2 name,
3 surname character (20),
3 given_name character (10),
2 address,
3 street character (20),
3 suburb character (20),
3 zip fixed decimal (7);
 
sub2: procedure() returns (type(customer));
declare c type (customer);
get edit (c.surname, c.given_name) (L);
get edit (c.street, c.suburb, c.zip) (L);
return (c);
end sub2;

Example 3 illustrates the return of two values as a complex value:

comp: procedure(a, b) returns (complex);
declare (a, b) float;
 
return (complex(a, b) );
end comp;

[edit] PureBasic

PureBasic's procedures return only a single value. The value needs to be a standard numeric type or string.

An array, map, or list can be used as a parameter to a procedure and in the process contain values to be returned as well. A pointer to memory or a structured variable may also be returned to reference multiple return values (requiring the memory to be manually freed afterwards).

;An array, map, or list can be used as a parameter to a procedure and in the
;process contain values to be returned as well.
Procedure example_1(x, y, Array r(1)) ;array r() will contain the return values
Dim r(2) ;clear and resize the array
r(0) = x + y ;return these values in the array
r(1) = x - y
r(2) = x * y
EndProcedure
 
;A pointer to memory or a structured variable may also be returned to reference
;multiple return values (requiring the memory to be manually freed afterwards).
Procedure example_2(x, y)
Protected *result.POINT = AllocateMemory(SizeOf(POINT))
*result\x = x
*result\y = y
 
ProcedureReturn *result ;*result points to a 'POINT' structure containing x and y
EndProcedure
 
If OpenConsole()
Dim a(5)
example_1(6, 5, a()) ;a() now contains {11, 1, 30}
PrintN("Array returned with {" + Str(a(0)) + ", " + Str(a(1)) + ", " + Str(a(2)) + "}")
 
Define *aPoint.POINT
*aPoint = example_2(6, 5) ;*aPoint references structured memory containing {6, 5}
 
PrintN("structured memory holds: (" + Str(*aPoint\x) + ", " + Str(*aPoint\y) + ")")
FreeMemory(*aPoint) ;freememory
 
Print(#CRLF$ + #CRLF$ + "Press ENTER to exit"): Input()
CloseConsole()
EndIf

[edit] Python

Every function returns one value. The conventional way to return multiple values is to bundle them into a tuple.

def addsub(x, y):
return x + y, x - y

(Note that parentheses are not necessary for a tuple literal in Python.)

You can assign to a comma-separated list of targets:

sum, difference = addsub(33, 12)
print "33 + 12 = %s" % sum
print "33 - 12 = %s" % difference

There is no discernable difference between "returning multiple values" and returning a single tuple of multiple values. It is just a more pedantic/accurate statement of the mechanism employed.

[edit] R

The conventional way to return multiple values is to bundle them into a list.

addsub <- function(x, y) list(add=(x + y), sub=(x - y))

[edit] Racket

Racket has a defined function "values" that returns multiple values using continuations, a way it can be implemented is shown in "my-values"

#lang racket
(values 4 5)
 
(define (my-values . return-list)
(call/cc
(lambda (return)
(apply return return-list))))

[edit] Raven

define multiReturn use $v
$v each
 
3 multiReturn
Output:
2
1
0

[edit] Retro

Functions take and return values via a stack. This makes returning multiple values easy.

: addSubtract ( xy-nm )
2over - [ + ] dip ;

[edit] REXX

Strictly speaking, REXX only returns one value (or no values), but the value (a string) can
comprise of multiple "values" or substrings.
If the multiple values are seperated by blanks [or some other unique character(s) such as
a comma, semicolon, blackslash, ...], it's a very simple matter to parse the multiple-value
string into the desired substrings (or values, if you will) with the handy-dandy PARSE statement.

/*REXX program shows examples of multiple RETURN values from a function.*/
numeric digits 70 /*default is: NUMERIC DIGITS 9 */
arg a b /*get 2 numbers from comand line.*/
say ' a =' a /*display the first number. */
say ' b =' b /* " " second " */
say copies('=',50) /*display a separator line. */
 
z=giveMeBackStuff(a,b) /*call function: giveMeBackStuff */
 
parse var z sum dif mod div idiv prod pow /*get the returned values,*/
prod=word(z,6) /*obtain an alternate way.*/
say ' + =' sum
say ' - =' dif
say '// =' mod
say ' / =' div
say ' % =' idiv
say ' * =' prod
say '** =' pow
exit /*stick a fork in it, we're done.*/
/*──────────────────────────────────giveMeBackStuff subroutine──────────*/
giveMeBackStuff: procedure; parse arg x,y
addition = x+y
subtract = x-y
modulus = x//y
divide = x/y
intDiv = x%y
multiply = x*y
power = x**y
return addition subtract modulus divide intDiv multiply power
/*──────────────────────────────────giveMeBackStuff2 subroutine─────────*/
giveMeBackStuff2: procedure; parse arg x,y
return x+y x-y x//y x/y x%y x*y x**y /*same as version above.*/

output when the following is used for input: 82 20

 a = 82
 b = 20
==================================================
 + = 102
 - = 62
// = 2
 / = 4.1
 % = 4
 * = 1640
** = 188919613181312032574569023867244773376

[edit] Ruby

Every function returns one value. The conventional way to return multiple values is to bundle them into an Array.

Use an array literal:

def addsub(x, y)
[x + y, x - y]
end

Or use return with 2 or more values:

def addsub(x, y)
return x + y, x - y
end

(With at least 2 values, return makes a new Array. With 1 value, return passes the value, without making any Array. With 0 values, return passes nil.)

Assignment can split the Array into separate variables.

sum, difference = addsub(33, 12)
puts "33 + 12 = #{sum}"
puts "33 - 12 = #{difference}"

[edit] Run BASIC

Courtesy http://dkokenge.com/rbp
Gets the UTC time from the web

a$ = timeInfo$()
print " UTC:";word$(a$,1,"|")
print "Date:";word$(a$,2,"|")
print "Time:";word$(a$,3,"|")
wait
function timeInfo$()
utc$ = word$(word$(httpget$("http://tycho.usno.navy.mil/cgi-bin/timer.pl"),1,"UTC"),2,"<BR>") ' Universal time
d$ = date$()
t$ = time$()
timeInfo$ = utc$;"|";d$;"|";t$
end function

[edit] Scala

Every function returns one value. The conventional way to return multiple values is to return a tuple.

def addsub(x: Int, y: Int) = (x + y, x - y)

You can use pattern matching to extract the components:

val (sum, difference) = addsub(33, 12)

Scala borrows this idea from ML, and generalizes it into extractors.

[edit] Scheme

Scheme can return multiple values using the values function, which uses continuations:

(define (addsub x y)
(values (+ x y) (- x y)))

You can use the multiple values using the call-with-values function:

(call-with-values
(lambda () (addsub 33 12))
(lambda (sum difference)
(display "33 + 12 = ") (display sum) (newline)
(display "33 - 12 = ") (display difference) (newline)))

The syntax is kinda awkward. SRFI 8 introduces a receive construct to make this simpler:

(receive (sum difference) (addsub 33 12)
; in this scope you can use sum and difference
(display "33 + 12 = ") (display sum) (newline)
(display "33 - 12 = ") (display difference) (newline))

SRFI 11 introduces a let-values construct to make this simpler:

(let-values (((sum difference) (addsub 33 12)))
; in this scope you can use sum and difference
(display "33 + 12 = ") (display sum) (newline)
(display "33 - 12 = ") (display difference) (newline))

[edit] Seed7

Seed7 functions can only return one value. That value could be an array or record holding multiple values, but the usual method for returning several values is using a procedure with inout parameters:

$ include "seed7_05.s7i";
 
const proc: sumAndDiff (in integer: x, in integer: y, inout integer: sum, inout integer: diff) is func
begin
sum := x + y;
diff := x - y;
end func;
 
const proc: main is func
local
var integer: sum is 0;
var integer: diff is 0;
begin
sumAndDiff(5, 3, sum, diff);
writeln("Sum: " <& sum);
writeln("Diff: " <& diff);
end func;
Output:
Sum: 8
Diff: 2

[edit] Standard ML

Every function returns one value. The conventional way to return multiple values is to return a tuple.

fun addsub (x, y) =
(x + y, x - y)

You can use pattern matching to extract the components:

let
val (sum, difference) = addsub (33, 12)
in
print ("33 + 12 = " ^ Int.toString sum ^ "\n");
print ("33 - 12 = " ^ Int.toString difference ^ "\n")
end

[edit] Tcl

Tcl commands all return a single value, but this value can be a compound value such as a list or dictionary. The result value of a procedure is either the value given to the return command or the result of the final command in the body in the procedure. (Commands that return “no” value actually return the empty string.)

proc addsub {x y} {
list [expr {$x+$y}] [expr {$x-$y}]
}

This can be then assigned to a single variable with set or to multiple variables with lassign.

lassign [addsub 33 12] sum difference
puts "33 + 12 = $sum, 33 - 12 = $difference"

[edit] TXR

TXR functions return material by binding unbound variables.

The following function potentially returns three values, which will happen if called with three arguments, each of which is an unbound variable:

@(define func (x y z))
@ (bind w "discarded")
@ (bind (x y z) ("a" "b" "c"))
@(end)

The binding w, if created, is discarded because w is not in the list of formal parameters. However, w can cause the function to fail because there can already exist a variable w with a value which doesn't match "discarded".

Call:

@(func t r s)

If t, r and s are unbound variables, they get bound to "a", "b" and "c", respectively via a renaming mechanism. This may look like C++ reference parameters or Pascal "var" parameters, and can be used that way, but isn't really the same at all.

Failed call ("1" doesn't match "a"):

@(func "1" r s)

Successful call binding only one new variable:

@(func "a" "b" s)

[edit] UNIX Shell

Shell scripts don't directly support returning values from a function, it can be simulated through some clunky code.

 
#!/bin/sh
funct1() {
a=$1
b=`expr $a + 1`
echo $a $b
}
 
values=`funct1 5`
 
set $values
x=$1
y=$2
echo "x=$x"
echo "y=$y"
 

Output produced:

x=5
y=6

[edit] XPL0

include c:\cxpl\codes;          \intrinsic 'code' declarations
 
proc Rect2Polar(X,Y,A,D); \Return two polar coordinate values
real X,Y,A,D;
[A(0):= ATan2(Y,X);
D(0):= Sqrt(X*X+Y*Y);
]; \Rect2Polar
 
real Ang, Dist;
[Rect2Polar(4.0, 3.0, @Ang, @Dist); \("@" is a new feature similar to 'addr')
RlOut(0, Ang);
RlOut(0, Dist);
CrLf(0);
]

Output (angle is in radians):

    0.64350    5.00000

[edit] zkl

fcn f{return(1,2,"three")}
a,b,c:=f() // a==1, b==2, c=="three"
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