## C++

C++ functions basically are the same as in C. Also macros exist, however they are discouraged in C++ in favour of inline functions and function templates.

An inline function differs from the normal function by the keyword inline and the fact that it has to be included in every translation unit which uses it (i.e. it normally is written directly in the header). It allows the compiler to eliminate the function without having the disadvantages of macros (like unintended double evaluation and not respecting scope), because the substitution doesn't happen at source level, but during compilation. An inline version of the above function is:

```cpp
inline double multiply(double a, double b)
{
   return a*b;
}

If not only doubles, but numbers of arbitrary types are to be multiplied, a function template can be used:

template<typename Number>

Number multiply(Number a, Number b)
{
   return a*b;
}

Of course, both inline and template may be combined (the inline then has to follow the template<...>), but since templates have to be in the header anyway (while the standard allows them to be compiled separately using the keyword export, almost no compiler implements that), the compiler usually can inline the template even without the keyword.

Clay

multiply(x,y) = x * y;

Clojure

(defn multiply [x y]
  (* x y))

(multiply 4 5)

Or with multiple arities (in the manner of the actual * function):

(defn multiply
  ([] 1)
  ([x] x)
  ([x y] (* x y))
  ([x y & more]
    (reduce * (* x y) more)))

(multiply 2 3 4 5)  ; 120

COBOL

In COBOL, ''multiply'' is a reserved word, so the requirements must be relaxed to allow a different function name. The following uses a program: {{works with|OpenCOBOL}}

       IDENTIFICATION DIVISION.
       PROGRAM-ID. myTest.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01  x   PIC 9(3) VALUE 3.
       01  y   PIC 9(3) VALUE 2.
       01  z   PIC 9(9).
       PROCEDURE DIVISION.
           CALL "myMultiply" USING
               BY CONTENT x, BY CONTENT y,
               BY REFERENCE z.
           DISPLAY z.
           STOP RUN.
       END PROGRAM myTest.

       IDENTIFICATION DIVISION.
       PROGRAM-ID. myMultiply.
       DATA DIVISION.
       LINKAGE SECTION.
       01  x   PIC 9(3).
       01  y   PIC 9(3).
       01  z   PIC 9(9).
       PROCEDURE DIVISION USING x, y, z.
           MULTIPLY x BY y GIVING z.
           EXIT PROGRAM.
       END PROGRAM myMultiply.

This example uses user-defined functions, which were added in COBOL 2002. {{works with|GNU Cobol|2.0}}

       IDENTIFICATION DIVISION.
       PROGRAM-ID. myTest.
       ENVIRONMENT DIVISION.
       CONFIGURATION SECTION.
       REPOSITORY.
           FUNCTION myMultiply.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01  x   PIC 9(3) VALUE 3.
       01  y   PIC 9(3) VALUE 2.
       PROCEDURE DIVISION.
           DISPLAY myMultiply(x, y).
           STOP RUN.
       END PROGRAM myTest.

       IDENTIFICATION DIVISION.
       FUNCTION-ID. myMultiply.
       DATA DIVISION.
       LINKAGE SECTION.
       01  x   PIC 9(3).
       01  y   PIC 9(3).
       01  z   pic 9(9).
       PROCEDURE DIVISION USING x, y RETURNING z.
           MULTIPLY x BY y GIVING z.
           EXIT FUNCTION.
       END FUNCTION myMultiply.

Coco

As CoffeeScript. In addition, Coco provides some syntactic sugar for accessing the arguments array reminiscent of Perl's @_:

multiply = -> @@0 * @@1

Furthermore, when no parameter list is defined, the first argument is available as it:

double = -> 2 * it

CoffeeScript

multiply = (a, b) -> a * b

ColdFusion

<cffunction name="multiply" returntype="numeric">
	<cfargument name="a" type="numeric">
	<cfargument name="b" type="numeric">
	<cfreturn a * b>
</cffunction>

Common Lisp

Common Lisp has ordinary functions and generic functions.

Ordinary Functions

Ordinary functions operate on the values of argument expressions. Lisp functions terminate by returning one or more values, or by executing a non-local dynamic control transfer, in which case values are not returned.

(defun multiply (a b)
  (* a b))

(multiply 2 3)

====User-Defined Compiler Optimization of Functions==== In Lisp we can express optimizations of calls to a function using compiler macros. For instance, suppose we know that the multiply function, which may be in another module, simply multiplies numbers together. We can replace a call to multiply by a constant, if the arguments are constant expressions. Like the usual kind of Lisp macro, the compiler macro takes the argument forms as arguments, not the argument values. The special keyword &whole gives the macro access to the entire expression, which is convenient for the unhandled cases, whereby no transformation takes place:

(define-compiler-macro multiply (&whole expr a b)
  (if (and (constantp a) (constantp b))
    (* (eval a) (eval b))
    expr)) ;; no macro recursion if we just return expr; the job is done!

Lisp implementations do not have to honor compiler macros. Usually compilers make use of them, but evaluators do not.

Here is test of the macro using a CLISP interactive session. Note that the multiply function is not actually defined, yet it compiles and executes anyway, which shows that the macro provided the translation something.

$ clisp -q
[1]> (define-compiler-macro multiply (&whole expr a b)
  (if (and (constantp a) (constantp b))
    (* (eval a) (eval b))
    expr))
MULTIPLY
[2]> (defun test1 () (multiply 2 3))
TEST1
[3]> (compile 'test1)
TEST1 ;
NIL ;
NIL
[4]> (disassemble 'test1)

Disassembly of function TEST1
(CONST 0) = 6
[ ... ]
2 byte-code instructions:
0     (CONST 0)                           ; 6
1     (SKIP&RET 1)
NIL
[5]> (test1)
6

Generic Functions

Lisp's generic functions are part of the object system. Generic functions are compiled to ordinary functions, and so are called in the ordinary way. Internally, however, they have the special behavior of dispatching one or more methods based on specializable parameters.

Methods can be defined right inside the DEFGENERIC construct, but usually are written with separate DEFMETHODS.

Also, the DEFGENERIC is optional, since the first DEFMETHOD will define the generic function, but good practice.

;;; terrific example coming

Creative Basic

DECLARE Multiply(N1:INT,N2:INT)

DEF A,B:INT

A=2:B=2

OPENCONSOLE

PRINT Multiply(A,B)

PRINT:PRINT"Press any key to close."

DO:UNTIL INKEY$<>""

CLOSECONSOLE

END

SUB Multiply(N1:INT,N2:INT)

     DEF Product:INT

     Product=N1*N2

RETURN Product

'Can also be written with no code in the subroutine and just RETURN N1*N2.

D

// A function:
int multiply1(int a, int b) {
    return a * b;
}

// Functions like "multiply1" can be evaluated at compile time if
// they are called where a compile-time constant result is asked for:
enum result = multiply1(2, 3); // Evaluated at compile time.
int[multiply1(2, 4)] array;    // Evaluated at compile time.

// A templated function:
T multiply2(T)(T a, T b) {
    return a * b;
}

// Compile-time multiplication can also be done using templates:
enum multiply3(int a, int b) = a * b;

pragma(msg, multiply3!(2, 3)); // Prints "6" during compilation.

void main() {
    import std.stdio;
    writeln("2 * 3 = ", result);
}

Both the compile-time and run-time output:

6
2 * 3 = 6

dc

For dc, the functions (called macros) are limited to names from 'a' to 'z' Create a function called 'm'

[*] sm

Use it (lm loads the function in 'm',x executes it, f shows the the stack.)

3 4 lm x f
= 12

Delphi

function Multiply(a, b: Integer): Integer;
begin
  Result := a * b;
end;

=={{header|Déjà Vu}}==

multiply a b:
    * a b

Dragon

def multiply(a, b) {
  return a*b
}

DWScript

function Multiply(a, b : Integer) : Integer;
begin
   Result := a * b;
end;

Dyalect

func multiply(a, b) {
    a * b
}

Using lambda syntax:

const multiply = (a, b) => a * b

Using shorthand function syntax:

const multiply = $0 * $1

E

def multiply(a, b) {
    return a * b
}

(This does not necessarily return a product, but whatever the "multiply" method of a returns. The parameters could be guarded to only accept standard numbers.)

It is also possible to write short anonymous function definitions which do not need explicit returns:

def multiply := fn a, b { a * b }

This definition is identical to the previous except that the function object will not know its own name.

EasyLang

func multiply a b . r . r = a * b . call multiply 7 5 res print res

## EchoLisp


```lisp

(define (multiply a b) (* a b)) → multiply ;; (1)
(multiply 1/3 666) → 222

;; a function is a lambda definition :
multiply
     → (λ (_a _b) (#* _a _b))

;; The following is the same as (1) :
(define multiply (lambda(a b) (* a b)))
multiply
    → (🔒 λ (_a _b) (#* _a _b)) ;; a closure


;; a function may be compiled
(lib 'compile)
(compile 'multiply "-float-verbose")
    →
💡 [0]     compiling _🔶_multiply ((#* _a _b))
;; object code (javascript) :
var ref,top = _blocks[_topblock];
/* */return (
/* */(_stack[top] *_stack[1 + top])
/* */);

multiply  → (λ (_a _b) (#🔶_multiply)) ;; compiled function

Efene

multiply = fn (A, B) {
    A * B
}

@public
run = fn () {
    io.format("~p~n", [multiply(2, 5)])
}

Eiffel

multiply(a, b: INTEGER): INTEGER
	do
		Result := a*b
	end

Ela

multiply x y = x * y

Anonymous function:

\x y -> x * y

Elena

real multiply(real a, real b)
        = a * b;

Anonymous function / closure:

symbol f := (x,y => x * y);

Root closure:

f(x,y){ ^ x * y }

Elixir

defmodule RosettaCode do
  def multiply(x,y) do
    x * y
  end

  def task, do: IO.puts multiply(3,5)
end

RosettaCode.task

{{out}}

15

Elm

--There are multiple ways to create a function in Elm

--This is a named function
multiply x y = x*y

--This is an anonymous function
\x y -> x*y

Emacs Lisp

(defun multiply (x y)
  (* x y))

A "docstring" can be added as follows. This is shown by the Emacs help system and is good for human users. It has no effect on execution.

(defun multiply (x y)
  "Return the product of X and Y."
  (* x y))

Erlang

% Implemented by Arjun Sunel
-module(func_definition).
-export([main/0]).

main() ->
	K=multiply(3,4),
	io :format("~p~n",[K]).

multiply(A,B) ->
	case {A,B} of
		{A, B} -> A * B
	end.

{{out}}

12
ok

ERRE

A statement function in ERRE is a '''single line''' function definition as in Fortran 77 or BASIC. These are useful in defining functions that can be expressed with a single formula. A statement function should appear in declaration part of the program. The format is simple - just type FUNCTION f(x,y,z,…) f=formula END FUNCTION

The main features of function statement are:

1. You can use relational operators, so it's possible to "compact" an IF THEN ELSE statement but not loop statements: you must use a procedure for these.

2. Functions can have their own identifier (integer, string, real,double).

3. It's possible to declare function with no parameter: use FUNCTION f()........

4. Functions always return '''one''' value.

5. ERRE for C-64 admits only real with one parameter functions.

FUNCTION MULTIPLY(A,B) MULTIPLY=A*B END FUNCTION

Usage:

IF MULTIPLY(A,B)>10 THEN ......

or

S=MULTIPLY(22,11)

Euphoria

function multiply( atom a, atom b )
    return a * b
end function

If you declare the arguments as object then sequence comprehension kicks in:

function multiply( object a, object b )
    return a * b
end function

sequence a = {1,2,3,4}
sequence b = {5,6,7,8}

? multiply( 9, 9 )
? multiply( 3.14159, 3.14159 )
? multiply( a, b )
? multiply( a, 7 )
? multiply( 10.39564, b )

{{out}}

81
9.869587728
{5,12,21,32}
{7,14,21,28}
{51.9782,62.37384,72.76948,83.16512}

=={{header|F Sharp|F#}}== The default will be an integer function but you can specify other types as shown:

let multiply x y = x * y // integer
let fmultiply (x : float) (y : float) = x * y

Factor

: multiply ( a b -- a*b ) * ;

Falcon

function sayHiTo( name )
 > "Hi ", name
end

FALSE

[*]     {anonymous function to multiply the top two items on the stack}
m:      {binding the function to one of the 26 available symbol names}
2 3m;!  {executing the function, yielding 6}

Fantom

class FunctionDefinition
{
  public static Void main ()
  {
    multiply := |Int a, Int b -> Int| { a * b }
    echo ("Multiply 2 and 4: ${multiply(2, 4)}")
  }
}

Fexl

\multiply=(\x\y * x y)

Or if I'm being cheeky:

\multiply=*

Fish

Functions cannot be named in Fish. However, they can be defined as new stacks that pull a certain number of arguments off the stack that came before. 2[ says pull 2 values off the stack and put them in a new, separate stack. ] says put all remaining values in the current stack onto the top of the stack below (the old stack).

2[*]

Forth

: fmultiply ( F: a b -- F: c )  F* ;
: multiply ( a b -- c )  * ;

Fortran

In FORTRAN I (1957), inline function could be defined at the beginning of the program. Let's note than to specify a floating point real the name of the statement function begins with an X (no type declaration) and to specify this is a function the name ends with a F.

     XMULTF(X,Y)=X*Y

And for interger multiplication:

     MULTF(I,J)=I*J

In FORTRAN IV, FORTRAN 66 or later, define a function:

FUNCTION MULTIPLY(X,Y)
REAL MULTIPLY, X, Y
MULTIPLY = X * Y
END

And for integer multiplication:

FUNCTION MULTINT(X,Y)
INTEGER MULTINT, X, Y
MULTINT = X * Y
END

In Fortran 95 or later, define an elemental function, so that this function can be applied to whole arrays as well as to scalar variables:

module elemFunc
contains
    elemental function multiply(x, y)
        real, intent(in) :: x, y
        real :: multiply
        multiply = x * y
    end function multiply
end module elemFunc

program funcDemo
    use elemFunc

    real :: a = 20.0, b = 30.0, c
    real, dimension(5) :: x = (/ 1.0, 2.0, 3.0, 4.0, 5.0 /), y = (/ 32.0, 16.0, 8.0, 4.0, 2.0 /), z

    c = multiply(a,b)     ! works with either function definition above

    z = multiply(x,y)     ! element-wise invocation only works with elemental function
end program funcDemo

It is worth noting that Fortran can call functions (and subroutines) using named arguments; e.g. we can call multiply in the following way:

c = multiply(y=b, x=a)   ! the same as multiply(a, b)
z = multiply(y=x, x=y)   ! the same as multiply(y, x)

(Because of commutativity property of the multiplication, the difference between multiply(x,y) and multiply(y,x) is not evident)

Also note that the function result can be declared with a different name within the routine:

module elemFunc
contains
    elemental function multiply(x, y) result(z)
        real, intent(in) :: x, y
        real :: z
        z = x * y
    end function multiply
end module elemFunc

FreeBASIC

' FB 1.05.0 Win64

Function multiply(d1 As Double, d2 As Double) As Double
  Return d1 * d2
End Function

This function could either be used for all numeric types (as they are implicitly convertible to Double) or could be overloaded to deal with each such type (there are 12 of them).

Alternatively, one could write a macro though this wouldn't be type-safe:

#Define multiply(d1, d2) (d1) * (d2)

Frink

multiply[x,y] := x*y

Futhark

{{incorrect|Futhark|Futhark's syntax has changed, so this example will not compile}}

fun multiply(x: int, y: int): int = x * y

FutureBasic

include "ConsoleWindow"

local fn multiply( a as long, b as long ) as long
end fn = a * b

print fn multiply( 3, 9 )

Output:

27

Gambas

'''[https://gambas-playground.proko.eu/?gist=bc93236474d9937217dd4117026f7441 Click this link to run this code]'''

Public Sub Main()

Print Multiply(56, 4.66)

End

Public Sub Multiply(f1 As Float, f2 As Float) As Float

Return f1 * f2

End

Output:

260.96

GAP

multiply := function(a, b)
    return a*b;
end;

GML

In GML one can not define a function but in [[Game Maker]] there is a ''script'' resource, which is the equivalent of a function as defined here. Scripts can be exported to or imported from a text file with the following format:

#define multiply
a = argument0
b = argument1
return(a * b)

Gnuplot

multiply(x,y) = x*y

# then for example
print multiply(123,456)

Go

Function return types in Go are statically typed and never depend on argument types.

The return statement can contain an expression of the function return type:

func multiply(a, b float64) float64 {
   return a * b
}

Alternatively, if the return value is named, the return statement does not require an expression:

func multiply(a, b float64) (z float64) {
   z = a * b
   return
}

Golfscript

{*}:multiply;

Groovy

def multiply = { x, y -> x * y }

Test Program:

println "x * y = 20 * 50 = ${multiply 20, 50}"

{{out}}

x * y = 20 * 50 = 1000

Halon

function multiply( $a, $b )
{
    return $a * $b;
}

Haskell

multiply x y = x * y

Alternatively, with help of auto-currying,

multiply = (*)

You can use [[lambda-function]]

multiply = \ x y -> x*y

Haxe

function multiply(x:Float, y:Float):Float{
   return x * y;
}

hexiscript

fun multiply a b
  return a * b
endfun

HicEst

FUNCTION multiply(a, b)
   multiply = a * b
END

HolyC

F64 Multiply(F64 a, F64 b) {
  return a * b;
}

F64 x;
x = Multiply(42, 13.37);
Print("%5.2f\n", x);

Hy

Function definition:

(defn multiply [a b]
  (* a b))

Lambda definition:

(def multiply (fn [a b] (* a b)))

i

concept multiply(a, b) {
	return a*b
}

=={{header|Icon}} and {{header|Unicon}}==

procedure multiply(a,b)
return a * b
end

IDL

The task description is unclear on what to do when the arguments to the function are non-scalar, so here's multiple versions:

function multiply ,a,b
  return, a* b
end

If "a" and "b" are scalar, this will return a scalar. If they are arrays of the same dimensions, the result is an array of the same dimensions where each element is the product of the corresponding elements in "a" and "b".

Alternatively, there's this possibility:

function multiply ,a,b
  return, product([a, b])
end

This will yield the same result for scalars, but if "a" and "b" are arrays it will return the product of all the elements in both arrays.

Finally, there's this option:

function multiply ,a,b
  return, a # b
end

This will return a scalar if given scalars, if given one- or two-dimensional arrays it will return the matrix-product of these arrays. E.g. if given two three-element one-dimensional arrays (i.e. vectors), this will return a 3x3 matrix.

Inform 6

[ multiply a b;
  return a * b;
];

Inform 7

To decide which number is (A - number) multiplied by (B - number):
	decide on A * B.

Io

multiply := method(a,b,a*b)

IWBASIC

'1. Not Object Oriented Program

DECLARE Multiply(N1:INT,N2:INT),INT

DEF A,B:INT

A=2:B=2

OPENCONSOLE

PRINT Multiply(A,B)

PRINT

'When compiled as a console only program, a press any key to continue is automatic.
CLOSECONSOLE

END

SUB Multiply(N1:INT,N2:INT),INT

     DEF Product:INT

     Product=N1*N2

RETURN Product
ENDSUB

'Can also be written with no code in the subroutine and just RETURN N1*N2.

----

'2. Not Object Oriented Program Using A Macro

$MACRO Multiply (N1,N2) (N1*N2)

DEF A,B:INT

A=5:B=5

OPENCONSOLE

PRINT Multiply (A,B)

PRINT

'When compiled as a console only program, a press any key to continue is automatic.
CLOSECONSOLE

END

----

'3. In An Object Oriented Program

CLASS Associate
'functions/methods
DECLARE Associate:'object constructor
DECLARE _Associate:'object destructor
'***Multiply declared***
DECLARE Multiply(UnitsSold:UINT),UINT
'members
DEF m_Price:UINT
DEF m_UnitsSold:UINT
DEF m_SalesTotal:UINT
ENDCLASS

DEF Emp:Associate

m_UnitsSold=10

Ass.Multiply(m_UnitsSold)

OPENCONSOLE

PRINT"Sales total: ",:PRINT"$"+LTRIM$(STR$(Emp.m_SalesTotal))

PRINT

CLOSECONSOLE

END

'm_price is set in constructor
SUB Associate::Multiply(UnitsSold:UINT),UINT
     m_SalesTotal=m_Price*UnitsSold
     RETURN m_SalesTotal
ENDSUB

SUB Associate::Associate()
     m_Price=10
ENDSUB

SUB Associate::_Associate()
'Nothing to cleanup
ENDSUB

J

multiply=: *

Works on conforming arrays of any rank (any number of dimensions, as long as the dimensions of one are a prefix of the dimensions of the other): atoms, lists, tables, etc.

Or, more verbosely (and a bit slower, though the speed difference should be unnoticeable in most contexts):

multiply=: dyad define
  x * y
)

Here we use an [http://www.jsoftware.com/help/dictionary/intro18.htm explicit] definition (where the arguments are named) rather than a [http://www.jsoftware.com/help/dictionary/intro19.htm tacit] version (where the arguments are implied). In explicit J verbs, x is the left argument and y is the right argument.

(Note, by the way, that explicit definitions are a subset of tacit definitions -- when the arguments are explicitly named they are still implied in the larger context containing the definition.)

Java

There are no global functions in Java. The equivalent is to define static methods in a class (here invoked as "Math.multiply(a,b)"). Overloading allows us to define the method for multiple types.

public class Math
{
     public static    int multiply(   int a,    int b) { return a*b; }
     public static double multiply(double a, double b) { return a*b; }
}

JavaScript

===ES1-*=== Function Declaration

function multiply(a, b) {
  return a*b;
}

===ES3-*=== Function Expression

var multiply = function(a, b) {
    return a * b;
};

Named Function Expression

var multiply = function multiply(a, b) {
    return a * b;
};

Method Definition

var o = {
  multiply: function(a, b) {
    return a * b;
  }
};

===ES5-*=== Accessors

var o = {
  get foo() {
    return 1;
  },
  set bar(value) {
    // do things with value
  }
};

===ES6-*=== Arrow Function

var multiply = (a, b) => a * b;
var multiply = (a, b) => { return a * b };

Concise Body Method Definition

var o = {
  multiply(a, b) {
    return a * b;
  }
};

Generator Functions

function * generator() {
  yield 1;
}

Joy

DEFINE multiply == * .

jq

Example of a simple function definition:

def multiply(a; b): a*b;

Example of the definition of an inner function:

# 2 | generate(. * .) will generate 2, 4, 16, 256, ...
def generate(f): def r: ., (f | r); r;

The previous example (generate/1) also illustrates that a function argument can be a function or composition of functions. Here is another example:

def summation(f): reduce .[] as $x (0; . + ($x|f));

summation/1 expects an array as its input and takes a function, f, as its argument. For example, if the input array consists of JSON objects with attributes "h" and "w", then to compute SIGMA (h * w) we could simply write:

summation( .h * .w)

Julia

{{works with|Julia|0.6}} General function definition:

function multiply(a::Number, b::Number)
  return a * b
end

Julia also supports assignment definition as shorthand:

multiply(a, b) = a * b

And lambda calculus:

multiply = (a, b) -> a * b

Kaya

program test;

// A function definition in Kaya:
Int multiply(Int a, Int b) {
    return a * b;
}

// And calling a function:
Void main() {
    putStrLn(string( multiply(2, 3) ));
}

Kotlin

// One-liner
fun multiply(a: Int, b: Int) = a * b

// Proper function definition
fun multiplyProper(a: Int, b: Int): Int {
    return a * b
}

Lasso

Lasso supports multiple dispatch — signature definitions determine which method will be invoked.

define multiply(a,b) => {
	return #a * #b
}

As this function is so simple it can also be represented like so:

define multiply(a,b) => #a * #b

Using multiple dispatch, different functions will be invoked depending on the functions input.

// Signatures that convert second input to match first input
define multiply(a::integer,b::any) => #a * integer(#b)
define multiply(a::decimal,b::any) => #a * decimal(#b)

// Catch all signature
define multiply(a::any,b::any) => decimal(#a) * decimal(#b)

LFE

(defun mutiply (a b)
  (* a b))

Liberty BASIC

'     define & call a function

print multiply( 3, 1.23456)

wait

function multiply( m1, m2)
    multiply =m1 *m2
end function

end

Lily

define multiply(a: Integer, b: Integer): Integer
{
  return a * b
}

Lingo

on multiply (a, b)
  return a * b
end

LiveCode

LiveCode has a built-in method called multiply, so there is an extra y to avoid an error.

function multiplyy n1 n2
    return n1 * n2
end multiplyy

put multiplyy(2,5) -- = 10

Locomotive Basic

10 DEF FNmultiply(x,y)=x*y
20 PRINT FNmultiply(2,PI)

Function names are always preceded by "FN" in Locomotive BASIC. Also, PI is predefined by the interpreter as 3.14159265.

Logo

to multiply :x :y
  output :x * :y
end

LSE64

multiply  : *
multiply. : *.  # floating point

Lua

function multiply( a, b )
    return a * b
end

Lucid

multiply(x,y) = x * y

M2000 Interpreter

A Module can return value

A module can return value to stack of values. Calling a module we place parent stack to module, so we can read any value.

Module Checkit {
      Module Multiply (a, b) {
            Push a*b
      }
      Multiply 10, 5
      Print Number=50

      Module Multiply {
            Push Number*Number
      }

      Multiply 10, 5
      Print Number=50
      \\ push before call
      Push 10, 5
      Multiply
      Read A
      Print A=50
      Push 10, 2,3 : Multiply : Multiply: Print Number=60
      Module Multiply {
            If not match("NN") Then Error "I nead two numbers"
            Read a, b
            Push a*b
      }
      Call Multiply 10, 5
      Print Number=50
      \\ now there are two values in stack 20 and 50
      Multiply
}
Call Checkit, 20, 50
Print Number=1000

A Local Function Definition

There are two types of function, the normal and the lambda. If a Function return string then we have to use $ at the end of function name.

Module Checkit {
      \\ functions can shange by using a newer definition
      \\ function Multiply is local, and at the exit of Checkit, erased.
      Function Multiply (a, b) {
            =a*b
      }
      Print Multiply(10, 5)=50

      Function Multiply {
            =Number*Number
      }

      Print Multiply(10, 5)=50

      Function Multiply {
            If not match("NN") Then Error "I nead two numbers"
            Read a, b
            =a*b
      }
      Print Multiply(10, 5)=50
      Function Multiply {
            Read a as long, b as long
            =a*b
      }
      Z=Multiply(10, 5)
      Print Z=50, Type$(Z)="Long"
      Function Multiply(a as decimal=1, b as decimal=2) {
            =a*b
      }
      D=Multiply(10, 5)
      Print D=50, Type$(D)="Decimal"
      D=Multiply( , 50)
      Print D=50, Type$(D)="Decimal"
      D=Multiply( 50)
      Print D=100, Type$(D)="Decimal"
      \\ by reference plus using type
      Function Multiply(&a as decimal, &b as decimal) {
            =a*b
            a++
            b--
      }
      alfa=10@
      beta=20@
      D=Multiply(&alfa, &beta)
      Print D=200, alfa=11,beta=19, Type$(D)="Decimal"
      \\ Using Match() to identify type of items at the top of stack
      Function MultiplyALot {
            M=Stack
            While Match("NN") {
                  mul=Number*Number
                  Stack M {
                        Data mul  ' at the bottom
                  }
            }
            =Array(M)
      }

      K=MultiplyALot(1,2,3,4,5,6,7,8,9,10)
      N=Each(K)
      While N {
            Print Array(N),     ' we get 2  12   30   56   90
      }
      Print
}
Checkit

A Lambda Function

Lambda function is first citizen. We can push it to stack and make another reading from stack. Lambda can use closures as static variables, some of them are pointers so if we copy a lambda we just copy the pointer. Pointers are containers like pointer to array, inventory and stack. Here we define string lambda function (there is a numeric also)

Module CheckIt {
      A$=Lambda$ N$="Hello There" (x) ->{
            =Mid$(N$, x)
      }
      Print A$(4)="lo There"
      Push A$
}
CheckIt
Read B$
Print B$(1)="Hello There"
Function List$ {
      Dim Base 1,   A$()
      A$()=Array$([])  ' make an array from stack items
      =lambda$ A$() (x) -> {
            =A$(x)
      }

}
\\ change definition/closures
B$=List$("Hello", "Rosetta", "Function")
Print B$(1)="Hello"

M4

define(`multiply',`eval($1*$2)')

multiply(2,3)

Make

In makefile, a function may be defined as a rule, with recursive make used to retrieve the returned value.

A=1
B=1

multiply:
   @expr $(A) \* $(B)

Invoking it

make -f mul.mk multiply A=100 B=3
> 300

Using gmake, the define syntax is used to define a new function {{works with|gmake}}

A=1
B=1

define multiply
   expr $(1) \* $(2)
endef

do:
   @$(call multiply, $(A), $(B))

|gmake -f mul.mk do A=5 B=3

Maple

multiply:= (a, b) -> a * b;

=={{header|Mathematica}} / {{header|Wolfram Language}}== There are two ways to define a function in Mathematica.

Defining a function as a transformation rule:

multiply[a_,b_]:=a*b

Defining a pure function:

multiply=#1*#2&

Maxima

f(a, b):= a*b;

MAXScript

fn multiply a b =
(
    a * b
)

Mercury

% Module ceremony elided...
:- func multiply(integer, integer) = integer.
multiply(A, B) = A * B.

Metafont

Metafont has macros, rather than functions; through those the language can be expanded. According to the kind of macro we are going to define, Metafont has different ways of doing it. The one suitable for this task is called primarydef.

primarydef a mult b = a * b enddef;

The '''primarydef''' allows to build binary operators with the same priority as *. For a more generic macro, we can use instead

```metafont
def mult(expr a, b) = (a * b) enddef;
t := mult(2,3);
show t;
end

min

' is syntax sugar for (), which is an anonymous function that takes two numbers from the data stack, multiplies them, and leaves the result on the data stack. To give it a name, we can use the : sigil which is syntax sugar for define.

'* :multiply

=={{header|МiniZinc}}==

function var int:multiply(a: var int,b: var int) =
    a*b;

=={{header|MK-61/52}}==

ИП0 ИП1 * В/О

Function (subprogram) that multiplies two numbers. Parameters in registers Р0 and Р1, the result (return value) in register X. Commands ''ИП0'' and ''ИП1'' cause the contents of the corresponding registers in the stack, the more they multiplied (command ''*'') and then code execution goes to the address from which the call subprogram (command ''В/О'').

=={{header|Modula-2}}==

PROCEDURE Multiply(a, b: INTEGER): INTEGER;
BEGIN
  RETURN a * b
END Multiply;

=={{header|Modula-3}}==

PROCEDURE Multiply(a, b: INTEGER): INTEGER =
BEGIN
  RETURN a * b;
END Multiply;

MUMPS

MULTIPLY(A,B);Returns the product of A and B
 QUIT A*B

Nanoquery

def multiply($a, $b)
    return ($a * $b)
end

Neko

var multiply = function(a, b) {
    a * b
}

$print(multiply(2, 3))

'''Output:''' 6

Nemerle

public Multiply (a : int, b : int) : int  // this is either a class or module method
{
    def multiply(a, b) { return a * b }   // this is a local function, can take advantage of type inference
    return multiply(a, b)
}

NESL

function multiply(x, y) = x * y;

The NESL system responds by reporting the type it has inferred for the function:

multiply = fn : (a, a) -> a :: (a in number)

NetRexx

/* NetRexx */
options replace format comments java crossref savelog symbols binary

pi      = 3.14159265358979323846264338327950
radiusY = 10
in2ft   = 12
ft2yds  = 3
in2mm   = 25.4
mm2m    = 1 / 1000
radiusM = multiply(multiply(radiusY, multiply(multiply(ft2yds, in2ft), in2mm)), mm2m)

say "Area of a circle" radiusY "yds radius: " multiply(multiply(radiusY, radiusY), pi).format(3, 3) "sq. yds"
say radiusY "yds =" radiusM.format(3, 3)  "metres"
say "Area of a circle" radiusM.format(3, 3)"m radius:" multiply(multiply(radiusM, radiusM), pi).format(3, 3)"m**2"


/**
 * Multiplication function
 */
method multiply(multiplicand, multiplier) public static returns Rexx

  product = multiplicand * multiplier
  return product

{{out}}

Area of a circle 10 yds radius:  314.159 sq. yds
10 yds =   9.144 metres
Area of a circle   9.144m radius: 262.677m**2

NewLISP

 (define (my-multiply a b) (* a b))
(lambda (a b) (* a b))
> (my-multiply 2 3)
6

Nial

Using variables

multiply is operation a b {a * b}

Using it

|multiply 2 3
=6

Point free form

mul is *

Using it

|mul 3 4
=12

Nial also allows creation of operators

multiply is op a b {a * b}

Using it.

|2 multiply 3
=6
|multiply 2 3
=6

Since this is an array programming language, any parameters can be arrays too

|mul 3 [1,2]
=3 6
|mul [1,2] [10,20]
=10 40

Nim

Nim has a magic variable, result, which can be used as a substitute for return. The result variable will be returned implicitly.

proc multiply(a, b: Int): Int =
  result = a * b

Here is the same function but with the use of the return keyword.

proc multiply(a, b: Int): Int =
  return a * b

The last statement in a function implicitly is the result value:

proc multiply(a, b: Int): Int = a * b

OASYS

method int multiply int x int y { return x * y }

## OASYS Assembler

OASYS Assembler requires a prefix and suffix on names to indicate their types (an omitted suffix means a void type).
<lang oasys_oaa>[&MULTIPLY#,A#,B#],A#<,B#<MUL RF

=={{header|Oberon-2}}== Oberon-2 uses procedures, and has a special procedure called a "Function Procedure" used to return a value.

PROCEDURE Multiply(a, b: INTEGER): INTEGER;
 BEGIN
    RETURN a * b;
 END Multiply;

Objeck

function : Multiply(a : Float, b : Float) ~, Float {
   return a * b;
}

OCaml

let int_multiply x y = x * y
let float_multiply x y = x *. y

Octave

function r = mult(a, b)
  r = a .* b;
endfunction

Oforth

Function #* is already defined : it removes 2 objects from the stack and returns on the stack the product of them.

If necessary, we can create a function with name multiply, but, it will just call *

: multiply  * ;

It is also possible to create a function with declared paramaters. In this case, if we define n parameters, n objects will be removed from the stack and stored into those parameters :

: multiply2(a, b)   a b * ;

A function return value (or values) is always what remains on the stack when the function ends. There is no syntax to define explicitely what is the return value(s) of a function.

Ol

Function creation implemented using keyword 'lambda'. This created anonymous function can be saved into local or global variable for further use.

(lambda (x y)
   (* x y))

Ol has two fully equal definitions of global named function (second one is syntactic sugar for first one). In fact both of them is saving the created lambda in global variable.

(define multiply (lambda (x y) (* x y)))

(define (multiply x y) (* x y))

And only one definition of local named functions (with immediate calculation). This type of definition helps to implement local recursions.

(let multiply ((x n) (y m))
   (* x y))

; example of naive multiplication function implementation using local recursion:
(define (multiply x y)
   (let loop ((y y) (n 0))
      (if (= y 0)
         n
         (loop (- y 1) (+ n x)))))

(print (multiply 7 8))
; ==> 56

OOC

multiply: func (a: Double, b: Double) -> Double {
  a * b
}

ooRexx

Internal Procedure

SAY multiply(5, 6)
EXIT
multiply:
    PROCEDURE
    PARSE ARG x, y
    RETURN x*y

::Routine Directive

say multiply(5, 6)
::routine multiply
    use arg x, y
    return x *y

Accomodate large factors

say multiply(123456789,987654321)
say multiply_long(123456789,987654321)
::routine multiply
    use arg x, y
    return x *y
::routine multiply_long
    use arg x, y
    Numeric Digits (length(x)+length(y))
    return x *y

{{out}}

1.21932631E+17
121932631112635269

OpenEdge/Progress

<lang Progress (Openedge ABL)>function multiply returns dec (a as dec , b as dec ): return a * b . end.

## Oz


```oz
fun {Multiply X Y}
   X * Y
end

Or by exploiting first-class functions:

Multiply = Number.'*'

PARI/GP

multiply(a,b)=a*b;

or

multiply=(a,b)->a*b;

Note that in both cases the ; is part of the definition of the function, not of the function itself: it suppresses the output of the function body, but does not suppress the output of the function when called. To do that, either double the semicolon (which will suppress the output of both) or wrap in braces:

multiply={(a,b)->a*b;}

which will return a function which calculates but does not return the product.

Pascal

(all versions and dialects)

function multiply(a,b: real): real;
begin
  multiply := a*b;
end;

Perl

The most basic form:

sub multiply { return $_[0] * $_[1] }

or simply:

sub multiply { $_[0] * $_[1] }

Arguments in Perl subroutines are passed in the @ array, and they can be accessed directly, first one as $[0], second one as $_[1], etc. When the above function is called with only one or no arguments then the missing ones have an undefined value which is converted to 0 in multiplication.

This is an example using [http://perldoc.perl.org/perlsub.html#Prototypes subroutine prototypes]:

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

The above subroutine can only be called with exactly two [http://perldoc.perl.org/perldata.html#Scalar-values scalar values] (two dollar signs in the signature) but those values may be not numbers or not even defined. The @_ array is unpacked into $a and $b lexical variables, which are used later.

The arguments can be automatically unpacked into lexical variables using the experimental signatures feature (in core as of 5.20):

use experimental 'signatures';
sub multiply ($x, $y) {
    return $x * $y;
}

Perl 6

Without a signature:

sub multiply { return @_[0] * @_[1]; }

The return is optional on the final statement, since the last expression would return its value anyway. The final semicolon in a block is also optional. (Beware that a subroutine without an explicit signature, like this one, magically becomes variadic (rather than nullary) only if @ or % appear in the body.) In fact, we can define the variadic version explicitly, which still works for two arguments:

sub multiply { [*] @_ }

With formal parameters and a return type:

sub multiply (Rat $a, Rat $b --> Rat) { $a * $b }

Same thing:

my Rat sub multiply (Rat $a, Rat $b) { $a * $b }

It is possible to define a function in "lambda" notation and then bind that into a scope, in which case it works like any function:

my &multiply := -> $a, $b { $a * $b };

Another way to write a lambda is with internal placeholder parameters:

my &multiply := { $^a * $^b };

(And, in fact, our original @ above is just a variadic self-declaring placeholder argument. And the famous Perl "topic", $, is just a self-declared parameter to a unary block.)

You may also curry both built-in and user-defined operators by supplying a * (known as "whatever") in place of the argument that is not to be curried:

my &multiply := * * *;

This is not terribly readable in this case due to the visual confusion between the whatever star and the multiplication operator, but Perl knows when it's expecting terms instead of infixes, so only the middle star is multiplication. It tends to work out much better with other operators. In particular, you may curry a cascade of methods with only the original invocant missing:

@list.grep( *.substr(0,1).lc.match(/<[0..9 a..f]>/) )

This is equivalent to:

@list.grep( -> $obj { $obj.substr(0,1).lc.match(/<[0..9 a..f]>/) } )

Phix

function multiply(atom a, atom b)
    return a*b
end function

PHL

@Integer multiply(@Integer a, @Integer b) [
	return a * b;
]

PHP

function multiply( $a, $b )
{
    return $a * $b;
}

Picat

multiply(A, B) = A*B.

PicoLisp

(de multiply (A B)
   (* A B) )

Pike

int multiply(int a, int b){
   return a * b;
}

PL/I

PRODUCT: procedure (a, b) returns (float);
   declare (a, b) float;
   return (a*b);
end PRODUCT;

PL/SQL

FUNCTION multiply(p_arg1 NUMBER, p_arg2 NUMBER) RETURN NUMBER
IS
  v_product NUMBER;
BEGIN
  v_product := p_arg1 * p_arg2;
  RETURN v_product;
END;

Pop11

define multiply(a, b);
    a * b
enddefine;

PostScript

Inbuilt:

Function would be:

```postscript
/multiply{
    /x exch def
    /y exch def
    x y mul =
}def

PowerShell

The most basic variant of function definition would be the kind which uses positional parameters and therefore doesn't need to declare much:

function multiply {
    return $args[0] * $args[1]
}

Also, the return statement can be omitted in many cases in PowerShell, since every value that "drops" out of a function can be used as a "return value":

function multiply {
    $args[0] * $args[1]
}

Furthermore, the function arguments can be stated and named explicitly:

function multiply ($a, $b) {
    return $a * $b
}

There is also an alternative style for declaring parameters. The choice is mostly a matter of personal preference:

function multiply {
    param ($a, $b)
    return $a * $b
}

And the arguments can have an explicit type:

function multiply ([int] $a, [int] $b) {
    return $a * $b
}

Processing

Processing is based on Java, and thus uses a familiar C-style syntax for function definition—as it does for much else. For the sake of argument, this implementation of multiply uses single-precision floats: other numeral types are available.

float multiply(float x, float y)
{
    return x * y;
}

Prolog

Prolog, as a logic programming languages, does not have user-supplied functions available. It has only predicates; statements which are "true" or "false". In cases where values have to be "returned" a parameter is passed in that is unified with the result. In the following predicate the parameter "P" (for "Product") is used in this role. The following code will work in any normal Prolog environment (but not in things like Turbo Prolog or Visual Prolog or their ilk):

multiply(A, B, P) :- P is A * B.

This is what it looks like in use:

go :-
  multiply(5, 2, P),
  format("The product is ~d.~n", [P]).

This can be a little bit jarring for those used to languages with implicit return values, but it has its advantages. For example unit testing of such a predicate doesn't require special frameworks to wrap the code:

test_multiply :-
  multiply(5, 2, 10),  % this will pass
  multiply(3, 4, 11).  % this will not pass

Still, the lack of user-defined functions remains an annoyance.

Prolog, however, is a remarkably malleable language and through its term re-writing capabilities the function-style approach could be emulated. The following code relies on the [http://packs.ndrix.com/function_expansion/index.html function_expansion] pack (separately installed through the packs system) for SWI-Prolog. Similar code could be made in any Prolog implementation, however.

:- use_module(library(function_expansion)).

user:function_expansion(multiply(A, B), P, P is A * B).  % "function" definition

go :-
  format("The product is ~d.~n", [multiply(5, 2)]).

While the function '''definition''' is perhaps a bit more involved, the function '''use''' is now pretty much the same as any other language people are used to. The "magic" is accomplished by the compiler rewriting the go/0 term into the following code:

go :-
  A is 5*2,
  format('The product is ~d.~n', [A]).

PureBasic

Procedure multiply(a,b)
  ProcedureReturn a*b
EndProcedure

Python

Function definition:

def multiply(a, b):
    return a * b

Lambda function definition:

multiply = lambda a, b: a * b

A callable class definition allows functions and classes to use the same interface:

class Multiply:
    def __init__(self):
        pass
    def __call__(self, a, b):
        return a * b

multiply = Multiply()
print multiply(2, 4)    # prints 8

(No extra functionality is shown in ''this'' class definition).

Q

multiply:{[a;b] a*b}

or

multiply:{x*y}

or

multiply:*

Using it

multiply[2;3]
 6

Quack

You have several ways to define a function in Quack. You can do it by the classic way:

fn multiply[ a; b ]
  ^ a * b
end

Using lambda-expressions:

let multiply :- fn { a; b | a * b }

And using partial anonymous functions:

let multiply :- &(*)

R

mult <- function(a,b) a*b

In general:

mult <- function(a,b) {
  a*b
  # or:
  # return(a*b)
}

Racket

A simple function definition that takes 2 arguments.

(define (multiply a b) (* a b))

Using an explicit lambda or λ is completely equivalent:

(define multiply (lambda (a b) (* a b)))

(define multiply (λ (a b) (* a b)))

Note that * is a function value, so the following code also works (although multiply will now be variadic function).

(define multiply *)

Raven

define multiply use a, b
    a b *

Or optional infix:

define multiply use a, b
    (a * b)

Or skip named vars:

define multiply *

REALbasic

Function Multiply(a As Integer, b As Integer) As Integer
  Return a * b
End Function

REBOL

REBOL actually already has a function called 'multiply', which is a native compiled function. However, since it's not protected, I can easily override it:

multiply: func [a b][a * b]

Retro

: multiply ( nn-n ) * ;

REXX

exactitudeness

multiply: return arg(1) * arg(2)    /*return the product of the two arguments.*/

cleaner display

Because REXX will return the same precision as the multiplicands, we can do some beautification with the resultant product.

I.E.: ''' 3.0 * 4.00 ''' yields the product: '''12.000'''

This version eliminates the '''.000''' from the product.

multiply: return arg(1) * arg(2) / 1    /*return with a normalized product of 2 args. */

RLaB

In RLaB the functions can be built-in (compiled within RLaB, or part of the shared object library that is loaded per request of user), or user (written in RLaB script). Consider an example:

 class(sin)
function
>> type(sin)
builtin

Functions are a data class on their own, or they can be member of a list (associative array).

1. user function specified from built-in functions, here basic addition

f = function(x, y)
{
  return x + y;
};

>> class(f)
function
>> type(f)
user

2. function can be member of a list (associative array)

;
somelist.f = function(x, y)
{
  rval = x + y;
  return rval;
};

3. user function which uses a function that is specified as a member of some list, here we use ''somelist'' from above:

g = function(x, y)
{
  global(somelist);
  rval = x * somelist.f(x, 2*y);
  return rval;
};

Ring

func multiply x,y return x*y

Ruby

def multiply(a, b)
    a * b
end

Rust

fn multiply(a: i32, b: i32) -> i32 {
    a * b
}

Sather

class MAIN is
  -- we cannot have "functions" (methods) outside classes
  mult(a, b:FLT):FLT is return a*b; end;

  main is
    #OUT + mult(5.2, 3.4) + "\n";
  end;
end;

=={{header|S-BASIC}}== S-BASIC is unusual in that the function return value is assigned to the END statement that terminates the function.

function multiply(a, b = real) = real
end = a * b

Scala

def multiply(a: Int, b: Int) = a * b

Scheme

(define multiply *)

Alternately,

(define (multiply a b)
  (* a b))

Seed7

const func float: multiply (in float: a, in float: b) is
  return a * b;

SETL

proc multiply( a, b );
    return a * b;
end proc;

Sidef

func multiply(a, b) {
    a * b;
}

Simula

Simula uses the term procedure for subroutines/methods whether they return a value or not. A procedure that does return a value is declared with a data type (e.g. integer procedure), whereas one that does not is declared simply as procedure. This program defines multiply as an integer procedure and illustrates its use. Note that the second argument provided to Outint gives the width of the integer to be printed.

BEGIN
    INTEGER PROCEDURE multiply(x, y);
    INTEGER x, y;
    BEGIN
        multiply := x * y
    END;
    Outint(multiply(7,8), 2);
    Outimage
END

Slate

define: #multiply -> [| :a :b | a * b].

or using a macro:

define: #multiply -> #* `er.

The block may also be installed as a method like so:

a@(Number traits) multiplyBy: b@(Number traits) [a * b].

or more explicitly (without sugar):

[| :a :b | a * b] asMethod: #multipleBy: on: {Number traits. Number traits}.

Smalltalk

|mul|
mul := [ :a :b | a * b ].

SNOBOL4

          define('multiply(a,b)') :(mul_end)
multiply  multiply = a * b        :(return)
mul_end
* Test
          output = multiply(10.1,12.2)
          output = multiply(10,12)
end

{{out}} 123.22 120

SNUSP

For expediency, the function is adding three values, instead of multiplying two values. Another function, atoi (+48) is called before printing the result.

+++3=@\==@\=.=#  prints '6'
        |        |   \=itoa=@@@+@+++++#
        \
### =
!\==!/===?\<#
                     \>+<-/

SPARK

The function definition (multiplies two standard Integer):

package Functions is
   function Multiply (A, B : Integer) return Integer;
   --# pre A * B in Integer; -- See note below
   --# return A * B; -- Implies commutativity on Multiply arguments
end Functions;

Note: how do you ensure then “A * B in Integer” ? Either with a proof prior to Multiply invokation or using another form of Multiply where input A and B would be restricted to a range which ensures the resulting product is always valid. Exemple :

type Input_Type is range 0 .. 10;
type Result_Type is range 0 .. 100;

and had a version of Multiply using these types. On the other hand, if arguments of Multiply are constants, this is provable straight away.

The Multiply's implementation:

package body Functions is
   function Multiply (A, B : Integer) return Integer is
   begin
      return A * B;
   end Multiply;
end Functions;

SPL

Single-line function definition:

multiply(a,b) <= a*b

Multi-line function definition:

multiply(a,b)=
  x = a*b
  <= x
.

SSEM

The SSEM instruction set makes no explicit provision for subroutines, and indeed its storage space is too small for them to be of much use; but something like a subroutine can be created using a modified form of Wheeler jump. In this technique, the jump to the subroutine is accomplished with the return address loaded in the accumulator. The first action by the subroutine is to store this address in a place where it will be found by its own final jump instruction. In principle, therefore, the subroutine can be called multiple times from different points in the program without the calling routine needing to modify it at all (or even to know anything about it beyond where it begins, where it expects to find its parameters, and where it will store its result or results).

In this example, the main routine does nothing at all beyond calling the subroutine and halting after it has returned. The values A and B are passed in the two addresses located immediately before the subroutine begins; their product is returned in the address that formerly stored A. Given that the multiply subroutine begins at address 8, the calling routine looks like this:

01000000000000100000000000000000   0. -2 to c
00100000000000000000000000000000   1. 4 to CI
01111111111111111111111111111111   2. -2
00000000000001110000000000000000   3. Stop
11100000000000000000000000000000   4. 7

or in pseudocode:

          load       &here
          jump       multiply
here:     halt

Implementing multiply on the SSEM requires the use of repeated negation and subtraction. For the sake of example, the values 8 and 7 are provided for A and B.

00010000000000000000000000000000   6. 8
11100000000000000000000000000000   7. 7
11111000000001100000000000000000   8. c to 31
01100000000000100000000000000000   9. -6 to c
01111000000001100000000000000000  10. c to 30
01111000000000100000000000000000  11. -30 to c
01111000000001100000000000000000  12. c to 30
11100000000000100000000000000000  13. -7 to c
11100000000001100000000000000000  14. c to 7
11100000000000100000000000000000  15. -7 to c
00111000000000010000000000000000  16. Sub. 28
11100000000001100000000000000000  17. c to 7
00111000000000010000000000000000  18. Sub. 28
00000000000000110000000000000000  19. Test
00111000000001000000000000000000  20. Add 28 to CI
11111000000000000000000000000000  21. 31 to CI
01100000000000100000000000000000  22. -6 to c
01111000000000010000000000000000  23. Sub. 30
01100000000001100000000000000000  24. c to 6
01100000000000100000000000000000  25. -6 to c
01100000000001100000000000000000  26. c to 6
10111000000000000000000000000000  27. 29 to CI
10000000000000000000000000000000  28. 1
00110000000000000000000000000000  29. 12
00000000000000000000000000000000  30. 0
00000000000000000000000000000000  31. 0

The pseudocode equivalent clarifies how the subroutine works, or how it would work on an architecture that supported load and add:

a:        equals     #8
b:        equals     #7
multiply: store      ret
          load       a
          store      n
loop:     load       b
          sub        #1
          store      b
          sub        #1
          ifNegative done
          load       a
          add        n
          store      a
          jump       loop
done:     jump       *ret
n:        reserve    1 word
ret:      reserve    1 word

Standard ML

val multiply = op *

Equivalently,

fun multiply (x, y) = x * y

Curried form:

fun multiply x y = x * y

Stata

Ado

Stata's macro language does not have functions, but commands. Output is usually saved as a "stored result" (but could also be saved in a global macro variable, in a scalar or matrix, in a dataset or simply printed to the Results window). See '''[https://www.stata.com/help.cgi?program program]''' and '''[https://www.stata.com/help.cgi?return]''' in Stata documentation.

prog def multiply, return
	args a b
	return sca product=`a'*`b'
end

multiply 77 13
di r(product)

'''Output'''

1001

Mata

Mata is the matrix language of Stata. Here is how to define a function

mata
scalar multiply(scalar x, scalar y) {
	return(x*y)
}

multiply(77,13)
end

'''Output'''

1001

Swift

func multiply(a: Double, b: Double) -> Double {
   return a * b
}

Tcl

Strictly as described in the task:

proc multiply { arg1 arg2 } {
    return [expr {$arg1 * $arg2}]
}

{{works with|Tcl|8.5}} You can also create functions that work directly inside expressions. This is done by creating the command with the correct name (that is, in the ''tcl::mathfunc'' namespace):

proc tcl::mathfunc::multiply {arg1 arg2} {
    return [expr {$arg1 * $arg2}]
}

# Demonstrating...
if {multiply(6, 9) == 42} {
    puts "Welcome, Citizens of Golgafrincham from the B-Ark!"
}

=={{header|TI-89 BASIC}}==

multiply(a, b)
Func
  Return a * b
EndFunc

Toka

[ ( ab-c ) * ] is multiply

TXR

In TXR, there are pattern functions which are predicates that perform pattern matching and variable capture. A call to this type of function call can specify unbound variables. If the function succeeds, it can establish bindings for those variables.

Here is how to make a pattern function that multiplies, and call it. To multiply the numbers, we break out of the pattern language and invoke Lisp evaluation: @(* a b)

@(define multiply (a b out))
@(bind out @(* a b))
@(end)
@(multiply 3 4 result)

$ txr -B multiply.txr
result="12"

In the embedded Lisp dialect, it is possible to write an ordinary function that returns a value:

(defun mult (a b) (* a b))
  (put-line `3 * 4 = @(mult 3 4)`)

$ txr multiply.tl
3 * 4 = 12

uBasic/4tH

In uBasic you can turn any subroutine into a function with the '''FUNC()''' function. It takes one argument, which is the label. Arguments are optional. PRINT FUNC (_Multiply (2,3)) END

_Multiply PARAM (2) RETURN (a@ * b@)

## UNIX Shell

Note that in the Unix shell, function definitions do not include any argument specifications within the parentheses. Instead arguments to functions are obtained using the positional parameters.
{{works with|Bourne Shell}}

```bash
multiply() {
  # There is never anything between the parentheses after the function name
  # Arguments are obtained using the positional parameters $1, and $2
  # The return is given as a parameter to the return command
  return `expr "$1" \* "$2"`    # The backslash is required to suppress interpolation
}

# Call the function
multiply 3 4    # The function is invoked in statement context
echo $?        # The dollarhook special variable gives the return value

{{works with|Bash}} return an exit code

multiply() {
  return $(($1 * $2))
}

multiply 5 6
echo $?

echo the result

multiply() {
  echo -n $(($1 * $2))
}

echo $(multiply 5 6)

Ursa

# multiply is a built-in in ursa, so the function is called mult instead
def mult (int a, int b)
	return (* a b)
end

Ursala

Functions are declared with an equals sign like constants of any other type. They may be specified by lambda abstraction, with dummy variables in double quotes, or in point-free form, or any combination. The way multiplication is defined depends on the type of numbers being multiplied. For this example, numbers in standard IEEE double precision are assumed, and the multiply function is defined in terms of the system library function, called using the syntax math..mul. This is the definition in point free form,

this is the definition using lambda abstraction

```Ursala
multiply = ("a","b"). math..mul ("a","b")

and this is the definition using pattern matching.

multiply("a","b") = math..mul ("a","b")

V

V uses stack for input arguments and '.' is a word that takes a quote and binds the first word to the sequence of actions supplied in the quote.

[multiply *].

Using it

2 3 multiply
=6

V also allows internal bindings.

[multiply
  [a b] let
  a b *].

VBA

Function Multiply(lngMcand As Long, lngMplier As Long) As Long
    Multiply = lngMcand * lngMplier
End Function

To use this function :

Sub Main()
Dim Result As Long
    Result = Multiply(564231, 897)
End Sub

VBScript

function multiply( multiplicand, multiplier )
    multiply = multiplicand * multiplier
end function

Usage:

dim twosquared
twosquared = multiply(2, 2)

Visual Basic

{{works with|Visual Basic|VB6 Standard}}

Function multiply(a As Integer, b As Integer) As Integer
    multiply = a * b
End Function

Call the function

Multiply(6, 111)

Visual Basic .NET

Function Multiply(ByVal a As Integer, ByVal b As Integer) As Integer
    Return a * b
End Function

Call the function

Multiply(1, 1)

Wart

A straightforward way to say how calls of the form (multiply a b) are translated:

def (multiply a b)
  a*b

(multiply 3 4)
=> 12

Functions can also use keyword args.

(multiply 3 :a 4)  # arg order doesn't matter here, but try subtract instead
=> 12

Finally, we can give parameters better keyword args using aliases:

def (multiply a b|by)
  (* a b)

multiply 3 :by 4
=> 12

X86 Assembly

X86 Assembly doesn't really have functions. Instead, it has labels that are called. Function arguments can be pushed onto the stack prior to calling or passed to the function in registers. The system will usually have some sort of calling conventions to facilitate inter-operation between languages.

Unix

Function definition and calling conventions on a Unix-like system are specified in the book "System V Application Binary Interface: Intel 386 Architecture Processor Supplement" ([https://web.archive.org/web/20000818171113/http://www.sco.com/developer/devspecs/abi386-4.pdf from SCO at archive.org]). These are the conventions used by the C language and also most other languages.

The stack, for two 32-bit integer parameters, is

• [esp+8] second parameter
• [esp+4] first parameter
• [esp] return address The return value is left in the eax register. ecx and edx are "scratch" registers meaning the called routine doesn't need to preserve their values. (In the code below edx is clobbered.)

The following is Unix-style "as" assembler syntax (including GNU as). The resulting function can be called from C with multiply(123,456).

        .text
        .globl  multiply
        .type   multiply,@function
multiply:
        movl    4(%esp), %eax
        mull    8(%esp)
        ret

The .type directive is important for code which will go into a shared library. You can get away without it for a static link. It ensures the linker knows to dispatch calls from the mainline to the function via a PLT entry. (If omitted the code is copied at runtime into some mainline space. Without a .size directive only 4 bytes will be copied.)

NASM

{{works with|NASM}}

section .text
global _start

_multiply_regs:
  mul ebx
  mov eax, ebx
  ret

_multiply_stack:
  enter 2,0
  mov eax, [esp+4]
  mov ebx, [esp+8]
  mul ebx
  mov eax, ebx
  leave
  ret

_start:
  mov ax, 6  ;The number to multiply by
  mov ebx, 16 ;base number to multiply.
  call _multiply_regs
  push 6
  push 16
  call _multiply_stack

MASM

However, in MASM we do have function statements due to the preprocessor. {{works with|MASM}}

multiply proc arg1:dword, arg2:dword
  mov eax, arg1
  mov ebx, arg2
  mul ebx
  mov eax, ebx
  ret
multiply endp

Then to call it.

invoke multiply, 6, 16
;or..
push 16
push 6
call multiply

Return values are usually put into the register EAX. This, of course is not a must it's simply that it's somewhat of a unofficial standard. For example, C/C++ preprocessors/compilers will translate "return value" into "mov eax, value" followed by the return to caller instruction "ret".

XLISP

Functions can be defined using either 'classic' Lisp syntax:

(defun multiply (x y)
    (* x y))

or Scheme-style syntax:

(define (multiply x y)
    (* x y))

or, if you prefer, with LAMBDA:

(define multiply
    (lambda (x y) (* x y)))

Xojo

Function Multiply(ByVal a As Integer, ByVal b As Integer) As Integer
    Return a * b
End Function

Call the function

Dim I As Integer = Multiply(7, 6)

XPL0

func Multiply(A, B);    \the characters in parentheses are only a comment
int  A, B;              \the arguments are actually declared here, as integers
return A*B;            \the default (undeclared) function type is integer
                        \no need to enclose a single statement in brackets

func real FloatMul(A, B); \floating point version
real A, B;              \arguments are declared here as floating point (doubles)
return A*B;

XSLT

Templates are the closest things XSLT has to user defined functions. They can be declared to be called by name and/or to be applied to all nodes in a matching set and given "mode". Both types of template can take named parameters with default values. Templates also have a "context" node used as the base of XPath expressions (kind of like an implied "this" of an object's method).

<xsl:template name="product">
  <xsl:param name="a" select="2"/>
  <xsl:param name="b" select="3"/>
  <fo:block>product = <xsl:value-of select="$a * $b"/></fo:block>
</xsl:template>

<xsl:call-template name="product">
  <xsl:with-param name="a">4</xsl:with-param>
  <xsl:with-param name="b">5</xsl:with-param>
</xsl:call-template>

<xsl:call-template name="product"/> <-- using default parameters of 2 and 3 -->

Yorick

func multiply(x, y) {
    return x * y;
}

Example of interactive usage:

> multiply(2, 4.5)
9

zkl

fcn multiply(x,y){x*y}

fcn(x,y){x*y}(4.5,3) // --> 13.5

Since all functions are vararg:

fcn multiply{vm.arglist.reduce('*)}
multiply(1,2,3,4,5) //--> 120

Operators are first class objects so:

var mul=Op("*"); mul(4,5) //-->20

ZX Spectrum Basic

On the ZX Spectrum, function names are limited to one letter. Note that the function becomes effective as soon as it is entered into the program, and does not need to be run

10 PRINT FN m(3,4): REM call our function to produce a value of 12
20 STOP
9950 DEF FN m(a,b)=a*b

{{omit from|GUISS}} {{omit from|TI-83 BASIC|Cannot define functions.}}