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Task

Take a combined set of elements and apply a function to each element.

11l

Translation of: Kotlin

V array = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
V arrsq = array.map(i -> i * i)
print(arrsq)

Output:

[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]

6502 Assembly

For this example, assume both the source array and the destination have a size of 86 elements (memory offsets base+0x00 to base+0x55.) This was implemented in easy6502.

define SRC_LO  $00
define SRC_HI  $01

define DEST_LO $02
define DEST_HI $03

define temp $04		;temp storage used by foo

;some prep work since easy6502 doesn't allow you to define arbitrary bytes before runtime.

SET_TABLE:
TXA
STA $1000,X
INX
BNE SET_TABLE	
;stores the identity table at memory address $1000-$10FF

CLEAR_TABLE:
LDA #0
STA $1200,X
INX
BNE CLEAR_TABLE
;fills the range $1200-$12FF with zeroes.


LDA #$10
STA SRC_HI
LDA #$00
STA SRC_LO
;store memory address $1000 in zero page

LDA #$12
STA DEST_HI
LDA #$00
STA DEST_LO
;store memory address $1200 in zero page


loop:
LDA (SRC_LO),y  ;load accumulator from memory address $1000+y
JSR foo		;multiplies accumulator by 3.
STA (DEST_LO),y ;store accumulator in memory address $1200+y

INY
CPY #$56 ;alternatively you can store a size variable and check that here instead.
BCC loop
BRK

foo:
STA temp
ASL		;double accumulator
CLC
ADC temp	;2a + a = 3a
RTS

Output:

1200: 00 03 06 09 0c 0f 12 15 18 1b 1e 21 24 27 2a 2d 
1210: 30 33 36 39 3c 3f 42 45 48 4b 4e 51 54 57 5a 5d 
1220: 60 63 66 69 6c 6f 72 75 78 7b 7e 81 84 87 8a 8d 
1230: 90 93 96 99 9c 9f a2 a5 a8 ab ae b1 b4 b7 ba bd 
1240: c0 c3 c6 c9 cc cf d2 d5 d8 db de e1 e4 e7 ea ed 
1250: f0 f3 f6 f9 fc ff

68000 Assembly

Translation of: 11l

The following assumes all code/data is stored/executed in RAM and is therefore mutable.

LEA MyArray,A0
MOVE.W #(MyArray_End-MyArray)-1,D7  ;Len(MyArray)-1
MOVEQ #0,D0 ;sanitize D0-D2 to ensure nothing from any previous work will affect our math.
MOVEQ #0,D1
MOVEQ #0,D2

loop:
MOVE.B (A0),D0
MOVE.B D0,D1
MOVE.B D0,D2
MULU D1,D2
MOVE.B D2,(A0)+
dbra d7,loop
jmp *       ;halt the CPU

MyArray:
DC.B 1,2,3,4,5,6,7,8,9,10
MyArray_End:

ACL2

ACL2 does not have first-class functions; this is close, however:

(defun apply-to-each (xs)
   (if (endp xs)
       nil
       (cons (fn-to-apply (first xs))
             (sq-each (rest xs)))))

(defun fn-to-apply (x)
   (* x x))

ActionScript

package
{
    public class ArrayCallback
    {
        public function main():void
        {
            var nums:Array = new Array(1, 2, 3);
            nums.map(function(n:Number, index:int, arr:Array):void { trace(n * n * n); });
            
            // You can also pass a function reference
            nums.map(cube);
        }
        
        private function cube(n:Number, index:int, arr:Array):void
        {
            trace(n * n * n);
        }
    }
}

Ada

Works with: GNAT version GPL 2005

with Ada.Text_Io;
 with Ada.Integer_text_IO;
 
 procedure Call_Back_Example is
    -- Purpose: Apply a callback to an array
    -- Output: Prints the squares of an integer array to the console
   
    -- Define the callback procedure
    procedure Display(Location : Positive; Value : Integer) is
    begin
       Ada.Text_Io.Put("array(");
       Ada.Integer_Text_Io.Put(Item => Location, Width => 1);
       Ada.Text_Io.Put(") = ");
       Ada.Integer_Text_Io.Put(Item => Value * Value, Width => 1);
       Ada.Text_Io.New_Line;
    end Display;
   
    -- Define an access type matching the signature of the callback procedure
    type Call_Back_Access is access procedure(L : Positive; V : Integer);
   
    -- Define an unconstrained array type
    type Value_Array is array(Positive range <>) of Integer;
   
    -- Define the procedure performing the callback
    procedure Map(Values : Value_Array; Worker : Call_Back_Access) is
    begin
       for I in Values'range loop
          Worker(I, Values(I));
       end loop;
    end Map;
   
    -- Define and initialize the actual array
    Sample : Value_Array := (5,4,3,2,1);
   
 begin
    Map(Sample, Display'access);   
 end Call_Back_Example;

Aime

void
map(list l, void (*fp)(object))
{
    l.ucall(fp, 0);
}

void
out(object o)
{
    o_(o, "\n");
}

integer
main(void)
{
    list(0, 1, 2, 3).map(out);

    return 0;
}

ALGOL 68

Works with: ALGOL 68 version Revision 1 - no extensions to language used

Works with: ALGOL 68G version Any - tested with release 1.18.0-9h.tiny

 PROC call back proc = (INT location, INT value)VOID:
 (
   printf(($"array["g"] = "gl$, location, value))
 );

 PROC map = (REF[]INT array, PROC (INT,INT)VOID call back)VOID:
 (
   FOR i FROM LWB array TO UPB array DO
      call back(i, array[i])
   OD
 );
 
 main:
 (
   [4]INT array := ( 1, 4, 9, 16 );
   map(array, call back proc)
 )

Output:

array[         +1] =          +1
array[         +2] =          +4
array[         +3] =          +9
array[         +4] =         +16

ALGOL W

begin
    procedure printSquare ( integer value x ) ; writeon( i_w := 1, s_w := 0, " ", x * x );
    % applys f to each element of a from lb to ub (inclusive) %
    procedure applyI ( procedure f; integer array a ( * ); integer value lb, ub ) ;
        for i := lb until ub do f( a( i ) );
    % test applyI %
    begin
        integer array a ( 1 :: 3 );
        a( 1 ) := 1; a( 2 ) := 2; a( 3 ) := 3;
        applyI( printSquare, a, 1, 3 )
    end
end.

APL

By default functions in APL work on arrays as it is an array oriented language. Some examples:

    - 1 2 3
¯1 ¯2 ¯3
    2 * 1 2 3 4
2 4 8 16
    2 × ⍳4
2 4 6 8
    3 * 3 3 ⍴ ⍳9
   3    9    27
  81  243   729
2187 6561 19683

AppleScript

on callback for arg
    -- Returns a string like "arc has 3 letters"
    arg & " has " & (count arg) & " letters"
end callback

set alist to {"arc", "be", "circle"}
repeat with aref in alist
    -- Passes a reference to some item in alist
    -- to callback, then speaks the return value.
    say (callback for aref)
end repeat

If the callback would set arg's contents to "something", then alist would be mutated.

For a more general implementation of map(function, list), foldl(function, startValue, list), and filter(predicate, list), we could write:

on run
    
    set xs to {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
    
    {map(square, xs), ¬
        filter(even, xs), ¬
        foldl(add, 0, xs)}
    
    --> {{1, 4, 9, 16, 25, 36, 49, 64, 81, 100}, {2, 4, 6, 8, 10}, 55}  
    
end run

-- square :: Num -> Num -> Num
on square(x)
    x * x
end square

-- add :: Num -> Num -> Num
on add(a, b)
    a + b
end add

-- even :: Int -> Bool
on even(x)
    0 = x mod 2
end even


-- GENERIC HIGHER ORDER FUNCTIONS

-- filter :: (a -> Bool) -> [a] -> [a]
on filter(f, xs)
    tell mReturn(f)
        set lst to {}
        set lng to length of xs
        repeat with i from 1 to lng
            set v to item i of xs
            if |λ|(v, i, xs) then set end of lst to v
        end repeat
        return lst
    end tell
end filter

-- foldl :: (a -> b -> a) -> a -> [b] -> a
on foldl(f, startValue, xs)
    tell mReturn(f)
        set v to startValue
        set lng to length of xs
        repeat with i from 1 to lng
            set v to |λ|(v, item i of xs, i, xs)
        end repeat
        return v
    end tell
end foldl

-- Lift 2nd class handler function into 1st class script wrapper 
-- mReturn :: First-class m => (a -> b) -> m (a -> b)
on mReturn(f)
    if class of f is script then
        f
    else
        script
            property |λ| : f
        end script
    end if
end mReturn

-- map :: (a -> b) -> [a] -> [b]
on map(f, xs)
    tell mReturn(f)
        set lng to length of xs
        set lst to {}
        repeat with i from 1 to lng
            set end of lst to |λ|(item i of xs, i, xs)
        end repeat
        return lst
    end tell
end map

Output:

{{1, 4, 9, 16, 25, 36, 49, 64, 81, 100}, {2, 4, 6, 8, 10}, 55}

Arturo

arr: [1 2 3 4 5]

print map arr => [2*&]

Output:

2 4 6 8 10

AutoHotkey

map("callback", "3,4,5")

callback(array){
  Loop, Parse, array, `,
    MsgBox % (2 * A_LoopField)
}
 
map(callback, array){
  %callback%(array)
}

AWK

$ awk 'func psqr(x){print x,x*x}BEGIN{split("1 2 3 4 5",a);for(i in a)psqr(a[i])}'
4 16
5 25
1 1
2 4
3 9

Babel

Let us define a squaring operator:

sq { dup * } <

Now, we apply the sq operator over a list and display the result using the lsnum utility:

( 0 1 1 2 3 5 8 13 21 34 ) { sq ! } over ! lsnum !

Output:

( 0 1 1 4 9 25 64 169 441 1156 )

BBC BASIC

Works with: BBC BASIC for Windows

      DIM a(4)
      a() = 1, 2, 3, 4, 5
      PROCmap(a(), FNsqrt())
      FOR i = 0 TO 4
        PRINT a(i)
      NEXT
      END
      
      DEF FNsqrt(n) = SQR(n)
      
      DEF PROCmap(array(), RETURN func%)
      LOCAL I%
      FOR I% = 0 TO DIM(array(),1)
        array(I%) = FN(^func%)(array(I%))
      NEXT
      ENDPROC

Output:

Binary Lambda Calculus

In the lambda calculus, we can map over a list as in https://github.com/tromp/AIT/blob/master/lists/map.lam, which gives the following BLC program to negate every bit of input:

010001101000000101100000000001011000000101111111010110010111111101111110111010

BQN

Square ← ×˜

array ← 2‿3‿5‿7‿11‿13

Square¨ array

The use of the ¨ modifier is the general approach, but actually not necessary with arithmetic functions.

Output:

⟨ 4 9 25 49 121 169 ⟩

Bracmat

( ( callbackFunction1
  =   location value
    .   !arg:(?location,?value)
      & out$(str$(array[ !location "] = " !!value))
  )
& ( callbackFunction2
  =   location value
    .   !arg:(?location,?value)
      & !!value^2:?!value
  )
& ( mapar
  =   arr len callback i
    .   !arg:(?arr,?len,?callback)
      & 0:?i
      &   whl
        ' ( !i:<!len
          & !callback$(!i,!i$!arr)
          & 1+!i:?i
          )
  )
& tbl$(array,4)
& 1:?(0$array)
& 2:?(1$array)
& 3:?(2$array)
& 4:?(3$array)
& mapar$(array,4,callbackFunction1)
& mapar$(array,4,callbackFunction2)
& mapar$(array,4,callbackFunction1)
);

Output:

array[0] = 1
array[1] = 2
array[2] = 3
array[3] = 4
array[0] = 1
array[1] = 4
array[2] = 9
array[3] = 16

Brat

#Print out each element in array
[:a :b :c :d :e].each { element |
	p element
}

Alternatively:

[:a :b :c :d :e].each ->p

C

callback.h

#ifndef CALLBACK_H
#define CALLBACK_H

/*
 * By declaring the function in a separate file, we allow
 * it to be used by other source files.
 *
 * It also stops ICC from complaining.
 *
 * If you don't want to use it outside of callback.c, this
 * file can be removed, provided the static keyword is prepended
 * to the definition.
 */
void map(int* array, int len, void(*callback)(int,int));

#endif

callback.c

#include <stdio.h>
#include "callback.h"

/*
 * We don't need this function outside of this file, so
 * we declare it static.
 */
static void callbackFunction(int location, int value)
{
  printf("array[%d] = %d\n", location, value);
} 

void map(int* array, int len, void(*callback)(int,int))
{
  int i;
  for(i = 0; i < len; i++)
  {
     callback(i, array[i]);
  }
} 

int main()
{
  int array[] = { 1, 2, 3, 4 };
  map(array, 4, callbackFunction);
  return 0;
}

Output:

  array[0] = 1
  array[1] = 2
  array[2] = 3
  array[3] = 4

C#

Works with: C# version 3.0+

This version uses the C# 3 lambda notation.

int[] intArray = { 1, 2, 3, 4, 5 };
// Simplest method:  LINQ, functional
int[] squares1 = intArray.Select(x => x * x).ToArray();

// Slightly fancier: LINQ, query expression
int[] squares2 = (from x in intArray
                  select x * x).ToArray();

// Or, if you only want to call a function on each element, just use foreach
foreach (var i in intArray)
    Console.WriteLine(i * i);

Works with: C# version 2.0+

Works with: Visual C# version 2005

using System; 

static class Program
{
  // Purpose: Apply a callback (or anonymous method) to an Array
  // Output: Prints the squares of an int array to the console.
  // Compiler: Visual Studio 2005
  // Framework: .net 2
   
  [STAThread]
  public static void Main() 
  {
    int[] intArray = { 1, 2, 3, 4, 5 };

    // Using a callback,
    Console.WriteLine("Printing squares using a callback:");
    Array.ForEach<int>(intArray, PrintSquare);

    // or using an anonymous method:
    Console.WriteLine("Printing squares using an anonymous method:");
    Array.ForEach<int>
    (
      intArray,
      delegate(int value) 
      {
        Console.WriteLine(value * value);    
      });
  }

  public static void PrintSquare(int value) 
  { 
    Console.WriteLine(value * value);
  }
}

C++

Works with: g++ version 4.1.1

C-Style Array

#include <iostream> //cout for printing
#include <algorithm> //for_each defined here

//create the function (print the square)
void print_square(int i) {
  std::cout << i*i << " ";
}

int main() {
  //create the array
  int ary[]={1,2,3,4,5};
  //stl for_each
  std::for_each(ary,ary+5,print_square);
  return 0;
}
//prints 1 4 9 16 25

std::vector

Library: STL

#include <iostream>  // cout for printing
#include <algorithm> // for_each defined here
#include <vector>    // stl vector class

// create the function (print the square)
void print_square(int i) {
  std::cout << i*i << " ";
}

int main() {
  // create the array
  std::vector<int> ary;
  ary.push_back(1);
  ary.push_back(2);
  ary.push_back(3);
  ary.push_back(4);
  ary.push_back(5);
  // stl for_each
  std::for_each(ary.begin(),ary.end(),print_square);
  return 0;
}
//prints 1 4 9 16 25

More tricky with binary function

#include <iostream>   // cout for printing
#include <algorithm>  // for_each defined here
#include <vector>     // stl vector class
#include <functional> // bind and ptr_fun

// create a binary function (print any two arguments together)
template<class type1,class type2>
void print_juxtaposed(type1 x, type2 y) {
  std::cout << x << y;
}

int main() {
  // create the array
  std::vector<int> ary;
  ary.push_back(1);
  ary.push_back(2);
  ary.push_back(3);
  ary.push_back(4);
  ary.push_back(5);
  // stl for_each, using binder and adaptable unary function
  std::for_each(ary.begin(),ary.end(),std::bind2nd(std::ptr_fun(print_juxtaposed<int,std::string>),"x "));
  return 0;
}
//prints 1x 2x 3x 4x 5x

Boost.Lambda

Library: Boost

using namespace std;
using namespace boost::lambda;
vector<int> ary(10);
int i = 0;
for_each(ary.begin(), ary.end(), _1 = ++var(i)); // init array
transform(ary.begin(), ary.end(), ostream_iterator<int>(cout, " "), _1 * _1); // square and output

C++11

#include <vector>
#include <iostream>
#include <algorithm>
#include <iterator>

int main() {
   std::vector<int> intVec(10);
   std::iota(std::begin(intVec), std::end(intVec), 1 ); // Fill the vector
   std::transform(std::begin(intVec) , std::end(intVec), std::begin(intVec),
	 [](int i) { return i * i ; } ); // Transform it with closures
   std::copy(std::begin(intVec), end(intVec) ,
	 std::ostream_iterator<int>(std::cout, " "));
   std::cout << std::endl;
   return 0;
}

Clean

Define a function and an initial (unboxed) array.

square x = x * x

values :: {#Int}
values = {x \\ x <- [1 .. 10]}

One can easily define a map for arrays, which is overloaded and works for all kinds of arrays (lazy, strict, unboxed).

mapArray f array = {f x \\ x <-: array}

Apply the function to the initial array (using a comprehension) and print result.

Start :: {#Int}
Start = mapArray square values

Clio

Math operations

[1 2 3 4] * 2 + 1 -> print

Quick functions

[1 2 3 4] -> * n: n * 2 + 1 -> print

Anonymous function

[1 2 3 4]
  -> * fn n:
     n * 2 + 1
  -> print

Named function

fn double-plus-one n:
  n * 2 + 1

[1 2 3 4] -> * double-plus-one -> print

Clojure

;; apply a named function, inc
(map inc [1 2 3 4])

;; apply a function
(map (fn [x] (* x x)) [1 2 3 4])

;; shortcut syntax for a function
(map #(* % %) [1 2 3 4])

CLU

% This procedure will call a given procedure with each element
% of the given array. Thanks to CLU's type parameterization,
% it will work for any type of element.
apply_to_all = proc [T: type] (a: array[T], f: proctype(int,T))
    for i: int in array[T]$indexes(a) do
        f(i, a[i])
    end
end apply_to_all

% Callbacks for both string and int
show_int = proc (i, val: int)
    po: stream := stream$primary_output()
    stream$putl(po, "array[" || int$unparse(i) || "] = " || int$unparse(val));
end show_int

show_string = proc (i: int, val: string)
    po: stream := stream$primary_output()
    stream$putl(po, "array[" || int$unparse(i) || "] = " || val);
end show_string

% Here's how to use them
start_up = proc () 
    po: stream := stream$primary_output()
    
    ints: array[int] := array[int]$[2, 3, 5, 7, 11]
    strings: array[string] := array[string]$
        ["enemy", "lasagna", "robust", "below", "wax"]
    
    stream$putl(po, "Ints: ")
    apply_to_all[int](ints, show_int)
    
    stream$putl(po, "\nStrings: ")
    apply_to_all[string](strings, show_string)
end start_up

Output:

Ints:
array[1] = 2
array[2] = 3
array[3] = 5
array[4] = 7
array[5] = 11

Strings:
array[1] = enemy
array[2] = lasagna
array[3] = robust
array[4] = below
array[5] = wax

COBOL

Works with: COBOL 2002

Basic implementation of a map function:

       >>SOURCE FORMAT IS FREE
IDENTIFICATION DIVISION.
PROGRAM-ID. map.

DATA DIVISION.
LOCAL-STORAGE SECTION.
01  i                  USAGE IS INDEX.
01  table-size         CONSTANT AS 30.
LINKAGE SECTION.
01  table-param.
    03 table-values    USAGE IS FLOAT-LONG, OCCURS table-size TIMES.
01  func-ptr           USAGE IS PROGRAM-POINTER.

PROCEDURE DIVISION USING BY REFERENCE table-param, BY VALUE func-ptr.
    PERFORM VARYING i FROM 1 BY 1 UNTIL i IS GREATER THAN table-size
        CALL func-ptr USING BY REFERENCE table-values(i)
    END-PERFORM
    GOBACK.

END PROGRAM map.

CoffeeScript

map = (arr, f) -> (f(e) for e in arr)
arr = [1, 2, 3, 4, 5]
f = (x) -> x * x
console.log map arr, f # prints [1, 4, 9, 16, 25]

Common Lisp

Imperative: print 1, 2, 3, 4 and 5:

(map nil #'print #(1 2 3 4 5))

Functional: collect squares into new vector that is returned:

(defun square (x) (* x x))
(map 'vector #'square #(1 2 3 4 5))

Destructive, like the Javascript example; add 1 to every slot of vector *a*:

(defvar *a* (vector 1 2 3))
(map-into *a* #'1+ *a*)

Component Pascal

BlackBox Component Builder

MODULE Callback;
IMPORT StdLog;

TYPE
	Callback = PROCEDURE (x: INTEGER;OUT doubled: INTEGER);
	Callback2 = PROCEDURE (x: INTEGER): INTEGER;
	
	PROCEDURE Apply(proc: Callback; VAR x: ARRAY OF INTEGER);
	VAR
		i: INTEGER;
	BEGIN
		FOR i := 0 TO LEN(x) - 1 DO;
			proc(x[i],x[i]);
		END
	END Apply;
	
	PROCEDURE Apply2(func: Callback2; VAR x: ARRAY OF INTEGER);
	VAR
		i: INTEGER;
	BEGIN
		FOR i := 0 TO LEN(x) - 1 DO;
			x[i] := func(x[i]);
		END
	END Apply2;
	
	PROCEDURE Double(x: INTEGER; OUT y: INTEGER);
	BEGIN	
		y := x * x;
	END Double;
	
	PROCEDURE Double2(x: INTEGER): INTEGER;
	BEGIN
		RETURN x * x
	END Double2;
	
	PROCEDURE Do*;
	VAR
		i: INTEGER;
		ary: ARRAY 10 OF INTEGER;
		
		
	BEGIN
		FOR i := 0 TO LEN(ary) - 1 DO ary[i] := i END;
		Apply(Double,ary);
		FOR i := 0 TO LEN(ary) - 1 DO
			StdLog.Int(ary[i]);StdLog.Ln
		END;
		StdLog.Ln;
		Apply2(Double2,ary);
		FOR  i := 0 TO LEN(ary) - 1 DO
		        StdLog.Int(ary[i]);StdLog.Ln
		END
	END Do;
END Callback.

Execute: ^Q Callback.Do

Output:

Crystal

Calling with a block

values = [1, 2, 3]

new_values = values.map do |number|
  number * 2
end

puts new_values  #=> [2, 4, 6]

Calling with a function/method

values = [1, 2, 3]

def double(number)
  number * 2
end

# the `->double(Int32)` syntax creates a proc from a function/method. argument types must be specified.
# the `&proc` syntax passes a proc as a block.
# combining the two passes a function/method as a block
new_values = values.map &->double(Int32)

puts new_values  #=> [2, 4, 6]

D

import std.stdio, std.algorithm;

void main() {
    auto items = [1, 2, 3, 4, 5];
    auto m = items.map!(x => x + 5)();
    writeln(m);
}

Output:

[6, 7, 8, 9, 10]

Delphi

// Declare the callback function
procedure callback(const AInt:Integer);
begin
  WriteLn(AInt);
end;

const
  // Declare a static array
  myArray:Array[0..4] of Integer=(1,4,6,8,7);
var
  // Declare interator variable
  i:Integer;
begin
  // Iterate the array and apply callback
  for i:=0 to length(myArray)-1 do
    callback(myArray[i]);
end.

Dyalect

func Array.Select(pred) {
    let ys = []
    for x in this when pred(x) {
        ys.Add(x)
    }
    return ys
}
 
var arr = [1, 2, 3, 4, 5]
var squares = arr.Select(x => x * x)
 
print(squares)

Déjà Vu

There is a map builtin that does just this.

!. map @++ [ 1 4 8 ]

#implemented roughly like this:
#map f lst:
#    ]
#    for i in lst:
#         f i
#    [

Output:

[ 2 5 9 ]

E

def array := [1,2,3,4,5]
def square(value) { 
    return value * value
}

Example of builtin iteration:

def callback(index, value) { 
    println(`Item $index is $value.`)
}
array.iterate(callback)

There is no built-in map function yet. The following is one of the ways one could be implemented, returning a plain list (which is usually an array in implementation).

def map(func, collection) {
    def output := [].diverge()
    for item in collection {
        output.push(func(item))
    }
    return output.snapshot()
}
println(map(square, array))

EchoLisp

(vector-map sqrt #(0 4 16 49))
    → #( 0 2 4 7)
;; or
(map exp #(0 1 2))
    → #( 1 2.718281828459045 7.38905609893065)
;; or
(for/vector ([elem #(2 3 4)] [i (in-naturals)]) (printf "v[%d] = %a" i elem) (* elem elem))
v[0] = 2
v[1] = 3
v[2] = 4
    → #( 4 9 16)

Efene

square = fn (N) {
    N * N
}

# list comprehension
squares1 = fn (Numbers) {
    [square(N) for N in Numbers]
}

# functional form
squares2a = fn (Numbers) {
    lists.map(fn square:1, Numbers)
}

# functional form with lambda
squares2b = fn (Numbers) {
    lists.map(fn (N) { N * N }, Numbers)
}

# no need for a function
squares3 = fn (Numbers) {
    [N * N for N in Numbers]
}

@public
run = fn () {
    Numbers = [1, 3, 5, 7]
    io.format("squares1 : ~p~n", [squares1(Numbers)])
    io.format("squares2a: ~p~n", [squares2a(Numbers)])
    io.format("squares2b: ~p~n", [squares2b(Numbers)])
    io.format("squares3 : ~p~n", [squares3(Numbers)])
}

EGL

delegate callback( i int ) returns( int ) end

program ApplyCallbackToArray
	function main()
		values int[] = [ 1, 2, 3, 4, 5 ];

		func callback = square;
		for ( i int to values.getSize() )
			values[ i ] = func( values[ i ] );
		end
		
		for ( i int to values.getSize() )
			SysLib.writeStdout( values[ i ] );
		end
	end
	
	function square( i int ) returns( int )
		return( i * i );
	end
end

Elena

ELENA 6.x :

import system'routines;

PrintSecondPower(n){ console.writeLine(n * n) }

public program()
{
    new int[]{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}.forEach(PrintSecondPower)
}

Elixir

Enum.map([1, 2, 3], fn(n) -> n * 2 end)
Enum.map [1, 2, 3], &(&1 * 2)

Output:

[2, 4, 6]

Erlang

A list would be more commonly used in Erlang rather than an array.

1> L = [1,2,3].
[1,2,3]

You can use lists:foreach/2 if you just want to apply the callback to each element of the list.

2> lists:foreach(fun(X) -> io:format("~w ",[X]) end, L).
1 2 3 ok

Or you can use lists:map/2 if you want to create a new list with the result of the callback on each element.

3> lists:map(fun(X) -> X + 1 end, L).
[2,3,4]

Or you can use lists:foldl/3 if you want to accumulate the result of the callback on each element into one value.

4> lists:foldl(fun(X, Sum) -> X + Sum end, 0, L).
6

ERRE

PROGRAM CALLBACK

!
! for rosettacode.org
!

DIM A[5]

FUNCTION CBACK(X)
   CBACK=2*X-1
END FUNCTION

PROCEDURE PROCMAP(ZETA,DUMMY(X)->OUTP)
   OUTP=DUMMY(ZETA)
END PROCEDURE

BEGIN
   A[1]=1  A[2]=2   A[3]=3  A[4]=4  A[5]=5
   FOR I%=1 TO 5 DO
      PROCMAP(A[I%],CBACK(X)->OUTP)
      PRINT(OUTP;)
   END FOR
   PRINT
END PROGRAM

This example shows how to pass a function to a procedure.

Output:

  1  3  5  7  9

Euphoria

function apply_to_all(sequence s, integer f)
    -- apply a function to all elements of a sequence
    sequence result
    result = {}
    for i = 1 to length(s) do
	-- we can call add1() here although it comes later in the program
	result = append(result, call_func(f, {s[i]}))
    end for
    return result
end function

function add1(atom x)
    return x + 1
end function

-- add1() is visible here, so we can ask for its routine id
? apply_to_all({1, 2, 3}, routine_id("add1"))
-- displays {2,3,4}

This is also "Example 2" in the Euphoria documentation for routine_id(). Note that this example will not work for multi-dimensional sequences.

F#

Apply a named function to each member of the array. The result is a new array of the same size as the input.

let evenp x = x % 2 = 0
let result = Array.map evenp [| 1; 2; 3; 4; 5; 6 |]

The same can be done using anonymous functions, this time squaring the members of the input array.

let result = Array.map (fun x -> x * x) [|1; 2; 3; 4; 5|]

Use iter if the applied function does not return a value.

Array.iter (fun x -> printfn "%d" x) [|1; 2; 3; 4; 5|]

Factor

Print each element squared:

{ 1 2 3 4 } [ sq . ] each

Collect return values:

{ 1 2 3 4 } [ sq ] map

Fantom

In Fantom, functions can be passed to a collection iterator, such as 'each'. 'map' is used similarly, and the results are collected into a list.

class Main
{
  public static Void main ()
  {
    [1,2,3,4,5].each |Int i| { echo (i) }
    Int[] result := [1,2,3,4,5].map |Int i->Int| { return i * i }
    echo (result) 
  }
}

Output:

1
2
3
4
5
[1, 4, 9, 16, 25]

FBSL

User-defined mapping function:

#APPTYPE CONSOLE

FOREACH DIM e IN MyMap(Add42, {1, 2, 3})
	PRINT e, " ";
NEXT

PAUSE

FUNCTION MyMap(f, a)
	DIM ret[]
	FOREACH DIM e IN a
		ret[] = f(e)
	NEXT
	RETURN ret
END FUNCTION

FUNCTION Add42(n): RETURN n + 42: END FUNCTION

Output:

43 44 45
Press any key to continue...

Standard MAP() function:

#APPTYPE CONSOLE

DIM languages[] = {{"English", {"one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten"}}, _
		  {"French", {"un", "deux", "trois", "quatre", "cinq", "six", "sept", "huit", "neuf", "dix"}}}

MAP(SpeakALanguage, languages)

PAUSE

SUB NameANumber(lang, nb, number)
	PRINT "The number ", nb, " is called ", STRENC(number), " in ", lang
END SUB

SUB SpeakALanguage(lang)
	MAP(NameANumber, lang[0], 1 TO 10, lang[1])
	PRINT LPAD("", 40, "-")
END SUB

Output:

The number 1 is called "one" in English
The number 2 is called "two" in English
The number 3 is called "three" in English
The number 4 is called "four" in English
The number 5 is called "five" in English
The number 6 is called "six" in English
The number 7 is called "seven" in English
The number 8 is called "eight" in English
The number 9 is called "nine" in English
The number 10 is called "ten" in English
----------------------------------------
The number 1 is called "un" in French
The number 2 is called "deux" in French
The number 3 is called "trois" in French
The number 4 is called "quatre" in French
The number 5 is called "cinq" in French
The number 6 is called "six" in French
The number 7 is called "sept" in French
The number 8 is called "huit" in French
The number 9 is called "neuf" in French
The number 10 is called "dix" in French
----------------------------------------
Press any key to continue...

Fe

(= map (fn (f lst)
  (let res (cons nil nil))
  (let tail res)
  (while lst
    (setcdr tail (cons (f (car lst)) nil))
    (= lst (cdr lst))
    (= tail (cdr tail)))
  (cdr res)))

(print (map (fn (x) (* x x)) '(1 2 3 4 5 6 7 8 9 10)))

Forth

This is a word that will call a given function on each cell in an array.

: map ( addr n fn -- )
   -rot cells bounds do  i @ over execute i !  cell +loop ;

Example usage:

create data 1 , 2 , 3 , 4 , 5 ,
data 5 ' 1+ map  \ adds one to each element of data

Fortran

Elemental functions.

Works with: Fortran version ISO 95 and later

module arrCallback
contains
    elemental function cube( x )
        implicit none
        real :: cube
        real, intent(in) :: x
        cube = x * x * x
    end function cube
end module arrCallback

program testAC
    use arrCallback
    implicit none
    integer :: i, j
    real, dimension(3,4) :: b, &
        a = reshape( (/ ((10 * i + j, i = 1, 3), j = 1, 4) /), (/ 3,4 /) )
     
    do i = 1, 3
        write(*,*) a(i,:)
    end do
     
    b = cube( a )  ! Applies CUBE to every member of a,
                   ! and stores each result in the equivalent element of b
    do i = 1, 3
        write(*,*) b(i,:)
    end do
end program testAC

Works with: ANSI FORTRAN version 77 (with MIL-STD-1753 structured DO) and later

      program test
C
C--   Declare array:
      integer a(5)
C
C--   Fill it with Data
      data a /45,22,67,87,98/
C
C--   Do something with all elements (in this case: print their squares)
      do i=1,5
        print *,a(i)*a(i)
      end do
C
      end

FP

{square * . [id, id]}
& square: <1,2,3,4,5>

FreeBASIC

' FB 1.05.0 Win64

Sub PrintEx(n As Integer)
  Print n, n * n, n * n * n
End Sub

Sub Proc(a() As Integer, callback As Sub(n As Integer))
  For i As Integer = LBound(a) To UBound(a)
    callback(i)
  Next
End Sub

Dim a(1 To 10) As Integer = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
Print " n", "n^2", "n^3"
Print " -", "---", "---"
Proc(a(), @PrintEx)
Print
Print "Press any key to quit the program"
Sleep

Output:

 n            n^2           n^3
 -            ---           ---
 1             1             1
 2             4             8
 3             9             27
 4             16            64
 5             25            125
 6             36            216
 7             49            343
 8             64            512
 9             81            729
 10            100           1000

Frink

f = {|x| x^2}   // Anonymous function to square input
a = [1,2,3,5,7]
println[map[f, a]]

FunL

[1, 2, 3].foreach( println )

[1, 2, 3].foreach( a -> println(2a) )

Output:

Futhark

map f l

e.g.

map (\x->x+1) [1,2,3] -- [2,3,4]

or equivalently

map (+1) [1,2,3] -- [2,3,4]

FutureBasic

include "NSLog.incl"

void local fn Callback( n as NSInteger )
  NSLog( @"Square root of %ld = %f", n, sqr(n) )
end fn

void local fn DoIt
  NSUInteger i, count
  CFArrayRef array = @[@1, @2, @3, @4, @5, @6, @7, @8, @9, @10]

  count = len(array)
  
  for i = 0 to count -1
    fn Callback( fn NumberIntegerValue( array[i] ) )
  next
end fn

fn DoIt

HandleEvents

Another option is to enumerate the array.

include "NSLog.incl"

void local fn Callback( array as CFArrayRef, obj as CFTypeRef )
  long value = intVal(obj)
  NSLog( @"Square root of %ld = %f", value, sqr(value) )
end fn

void local fn DoIt
  CFArrayRef array = @[@1, @2, @3, @4, @5, @6, @7, @8, @9, @10]
  ArrayEnumerateObjects( array, @fn Callback, NULL )
end fn

fn DoIt

HandleEvents

Output:

Square root of 1 = 1.000000
Square root of 2 = 1.414214
Square root of 3 = 1.732051
Square root of 4 = 2.000000
Square root of 5 = 2.236068
Square root of 6 = 2.449490
Square root of 7 = 2.645751
Square root of 8 = 2.828427
Square root of 9 = 3.000000
Square root of 10 = 3.162278

Fōrmulæ programs are not textual, visualization/edition of programs is done showing/manipulating structures but not text. Moreover, there can be multiple visual representations of the same program. Even though it is possible to have textual representation —i.e. XML, JSON— they are intended for storage and transfer purposes more than visualization and edition.

Programs in Fōrmulæ are created/edited online in its website.

In this page you can see and run the program(s) related to this task and their results. You can also change either the programs or the parameters they are called with, for experimentation, but remember that these programs were created with the main purpose of showing a clear solution of the task, and they generally lack any kind of validation.

Solution

Most programming languages define a high-order map function. In Fōrmulæ, there is arraization (by analogy with summation). In the following expression, the "big" curly braces resembles the "big" sigma of a summation:

The elements of the array are not required to be of the same type:

GAP

a := [1 .. 4];
b := ShallowCopy(a);

# Apply and replace values
Apply(a, n -> n*n);
a;
# [ 1, 4, 9, 16 ]

# Apply and don't change values
List(b, n -> n*n);
# [ 1, 4, 9, 16 ]

# Apply and don't return anything (only side effects)
Perform(b, Display);
1
2
3
4

b;
# [ 1 .. 4 ]

Go

Translation of: Ruby

The task was originally written with a Ruby example, so here are Go versions of the current Ruby examples.

Perhaps in contrast to Ruby, it is idiomatic in Go to use the for statement:

package main

import "fmt"

func main() {
    for _, i := range []int{1, 2, 3, 4, 5} {
        fmt.Println(i * i)
    }
}

Alternatively though, an array-like type can be defined and callback-style methods can be defined on it to apply a function to the elements.

package main

import "fmt"

type intSlice []int

func (s intSlice) each(f func(int)) {
    for _, i := range s {
        f(i)
    }
}

func (s intSlice) Map(f func(int) int) intSlice {
    r := make(intSlice, len(s))
    for j, i := range s {
        r[j] = f(i)
    }
    return r
}

func main() {
    s := intSlice{1, 2, 3, 4, 5}

    s.each(func(i int) {
        fmt.Println(i * i)
    })

    fmt.Println(s.Map(func(i int) int {
        return i * i
    }))
}

Output:

1
4
9
16
25
[1 4 9 16 25]

Groovy

Print each value in a list

[1,2,3,4].each { println it }

Create a new list containing the squares of another list

[1,2,3,4].collect { it * it }

Haskell

List

Works with: GHC

let square x = x*x
let values = [1..10]
map square values

Using list comprehension to generate a list of the squared values

[square x | x <- values]

More directly

[1 .. 10] >>= pure . (^ 2)

Or with one less layer of monadic wrapping

(^ 2) <$> [1..10]

Using function composition to create a function that will print the squares of a list

let printSquares = mapM_ (print.square)
printSquares values

Array

Works with: GHC version 7.10.3

import Data.Array (Array, listArray)

square :: Int -> Int
square x = x * x

values :: Array Int Int
values = listArray (1, 10) [1 .. 10]

main :: IO ()
main = print $ fmap square values

Output:

array (1,10) [(1,1),(2,4),(3,9),(4,16),(5,25),(6,36),(7,49),(8,64),(9,81),(10,100)]

Guish

Works with: guish version 2.5.1

# applies add2 (adds 2) to each element
add2 = {
    return add(@1, 2)
}
l = {1, 2, 3, 4, 5, 6, 7}
puts each(add2, flat(@l))

Icon and Unicon

procedure main()
   local lst
   lst := [10, 20, 30, 40]
   every callback(write,!lst)
end

procedure callback(p,arg)
   return p(" -> ", arg)
end

IDL

Hard to come up with an example that isn't completely contrived. IDL doesn't really distinguish between a scalar and an array; thus

b = a^3

will yield a scalar if a is scalar or a vector if a is a vector or an n-dimensional array if a is an n-dimensional array

Insitux

; apply a named function
(map inc [1 2 3 4])

; apply a parameterised closure
(map (fn x (+ x 1)) [1 2 3 4])

; apply a non-parameterised closure
(map #(+ % 1) [1 2 3 4])

; apply an explicit partial closure
(map @(+ 1) [1 2 3 4])

; apply an implicit partial closure
(map (+ 1) [1 2 3 4])

Io

list(1,2,3,4,5) map(squared)

J

Solution:

"_1

Example:

   callback =:  *:
   array    =:  1 2 3 4 5
   
   callback"_1 array
1 4 9 16 25

But note that this is a trivial example since *: 1 2 3 4 5 would get the same result. Then again, this is something of a trivial exercise in J since all of J is designed around the idea of applying functions usefully to arrays.

Jakt

fn map<T, U>(anon array: [T], function: fn(anon x: T) -> U) throws -> [U] {
    mut result: [U] = []
    result.ensure_capacity(array.size())
    for item in array {
        result.push(value: function(item))
    }
    return result
}

fn main() {
    let array = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
    let array_squared = map(array, function: fn(anon n: i64) => n * n)
    println("{}", array_squared)
}

Output:

[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]

Java

Up to Java 7, you have to define an interface for each type of function you want to use. The IntConsumer performs an action (which doesn't return anything) on an array of ints, while the IntToInt is used to replace the array values.

public class ArrayCallback7 {

    interface IntConsumer {
        void run(int x);
    }

    interface IntToInt {
        int run(int x);
    }

    static void forEach(int[] arr, IntConsumer consumer) {
        for (int i : arr) {
            consumer.run(i);
        }
    }

    static void update(int[] arr, IntToInt mapper) {
        for (int i = 0; i < arr.length; i++) {
            arr[i] = mapper.run(arr[i]);
        }
    }

    public static void main(String[] args) {
        int[] numbers = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

        forEach(numbers, new IntConsumer() {
            public void run(int x) {
                System.out.println(x);
            }
        });

        update(numbers, new IntToInt() {
            @Override
            public int run(int x) {
                return x * x;
            }
        });

        forEach(numbers, new IntConsumer() {
            public void run(int x) {
                System.out.println(x);
            }
        });
    }
}

Using Java 8 streams:

Works with: Java version 8

import java.util.Arrays;

public class ArrayCallback {

    public static void main(String[] args) {
        int[] myIntArray = {1, 2, 3, 4, 5};

        int sum = Arrays.stream(myIntArray)
                .map(x -> {
                    int cube = x * x * x;
                    System.out.println(cube);
                    return cube;
                })
                .reduce(0, (left, right) -> left + right); // <-- could substitute .sum() for .reduce(...) here.
        System.out.println("sum: " + sum);
    }
}

JavaScript

ES3

function map(a, func) {
  var ret = [];
  for (var i = 0; i < a.length; i++) {
    ret[i] = func(a[i]);
  }
  return ret;
}

map([1, 2, 3, 4, 5], function(v) { return v * v; });

ES5

[1, 2, 3, 4, 5].map(function(v) { return v * v; });

ES6

[1, 2, 3, 4, 5].map(v => v * v);

The result is always:

[1, 4, 9, 16, 25]

Joy

[1 2 3 4 5] [dup *] map.

jq

# Illustration of map/1 using the builtin filter: exp
map(exp)  # exponentiate each item in the input list

# A compound expression can be specified as the argument to map, e.g.
map( (. * .) + sqrt ) # x*x + sqrt(x)

# The compound expression can also be a composition of filters, e.g.
map( sqrt|floor )     # the floor of the sqrt

# Array comprehension
reduce .[] as $n ([]; . + [ exp ])

# Elementwise operation 
 [.[] + 1 ]   # add 1 to each element of the input array

Here is a transcript illustrating how the last of these jq expressions can be evaluated:

$ jq -c ' [.[] + 1 ]'
[0, 1 , 10]
[1,2,11]

Jsish

/* Apply callback, in Jsish using array.map() */
;[1, 2, 3, 4, 5].map(function(v,i,a) { return v * v; });

/*
=!EXPECTSTART!=
[1, 2, 3, 4, 5].map(function(v,i,a) { return v * v; }) ==> [ 1, 4, 9, 16, 25 ]
=!EXPECTEND!=
*/

Output:

prompt$ jsish -u applyCallback.jsi
[PASS] applyCallback.jsi

Julia

Works with: Julia version 0.6

numbers = [1, 3, 5, 7]

@show [n ^ 2 for n in numbers]                  # list comprehension
square(x) = x ^ 2; @show map(square, numbers)   # functional form
@show map(x -> x ^ 2, numbers)                  # functional form with anonymous function
@show [n * n for n in numbers]    				# no need for a function,
@show numbers .* numbers                        # element-wise operation
@show numbers .^ 2                              # includes .+, .-, ./, comparison, and bitwise operations as well

Kotlin

fun main(args: Array<String>) {
    val array = arrayOf(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)  // build
    val function = { i: Int -> i * i } // function to apply
    val list = array.map { function(it) } // process each item
    println(list) // print results
}

Output:

[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]

Klingphix

include ..\Utilitys.tlhy

( 1 2 3 4 ) [dup *] map

pstack

" " input

Output:

((1, 4, 9, 16))

Lambdatalk

{A.map {lambda {:x} {* :x :x}} {A.new 1 2 3 4 5 6 7 8 9 10}}
-> [1,4,9,16,25,36,49,64,81,100]

Lang

&arr = fn.arrayGenerateFrom(fn.inc, 10)
fn.println(&arr)
fn.arrayMap(&arr, fn.combC(fn.pow, 2))
fn.println(&arr)

Output:

[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]

Lang5

: square(*)  dup * ;
[1 2 3 4 5] square        . "\n" .
[1 2 3 4 5] 'square apply . "\n" .

langur

writeln map fn{^2}, 1..10

Output:

[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]

Lasso

define cube(n::integer) => #n*#n*#n

local(
	mynumbers = array(1, 2, 3, 4, 5),
	mycube = array
)

#mynumbers -> foreach => {
	#mycube -> insert(cube(#1))
}

#mycube

-> array(1, 8, 27, 64, 125)

Lisaac

+ a : ARRAY(INTEGER);
+ b : {INTEGER;};

a := ARRAY(INTEGER).create 1 to 3;
1.to 3 do { i : INTEGER;
  a.put i to i;
};

b := { arg : INTEGER;
  (arg * arg).print;
  '\n'.print;
};

a.foreach b;

Logo

to square :x
  output :x * :x
end
show map "square [1 2 3 4 5]  ; [1 4 9 16 25]
show map [? * ?] [1 2 3 4 5]  ; [1 4 9 16 25]
foreach [1 2 3 4 5] [print square ?]  ; 1 4 9 16 25, one per line

Lua

Say we have an array:

myArray = {1, 2, 3, 4, 5}

A map function for this would be

map = function(f, data)
   local result = {}
   for k,v in ipairs(data) do
      result[k] = f(v)
   end
   return result
end

Together with our array and a square function this yields:

myFunc = function(x) return x*x end

print(unpack( map(myFunc, myArray) ))
--> 1   4   9   16  25

If you used pairs() instead of ipairs(), this would even work on a hash table in general. However, remember that hash table do not have an implicit ordering on their elements, like arrays do, so pairs() is not guaranteed to return the elements in the same order as ipairs()

M2000 Interpreter

a=(1,2,3,4,5)
b=lambda->{
	push number**2	
}
Print a#map(b) ' 1 4 9 16 25
Print a#map(b, b)  ' 1 16 81 256 625
b=lambda (z) ->{
	=lambda z ->{
		push number**z	
	}	
}
Print a#map(b(2)) ' 1 4 9 16 25
Print a#map(b(3)) ' 1 8 27 64 125

\\ second example
a=(1,2,3,4,5)
class s {sum=0}
\\ s is a pointer to an instance of s()
s->s()
c=lambda s -> {
	push number+number
	s=>sum=stackitem()  ' peek the value from stack
}
\\ c passed by value to fold(), but has a pointer to s
Print a#fold(c, 100)=115
Print s=>sum=115

M4

define(`foreach', `pushdef(`$1')_foreach($@)popdef(`$1')')dnl
define(`_arg1', `$1')dnl
define(`_foreach', `ifelse(`$2', `()', `',
   `define(`$1', _arg1$2)$3`'$0(`$1', (shift$2), `$3')')')dnl
dnl
define(`apply',`foreach(`x',$1,`$2(x)')')dnl
dnl
define(`z',`eval(`$1*2') ')dnl
apply(`(1,2,3)',`z')

Output:

2 4 6

Maple

For lists and sets, which in Maple are immutable, a new object is returned. Either the built-in procedure map, or the short syntax of a trailing tilde (~) on the applied operator may be used.

> map( sqrt, [ 1.1, 3.2, 5.7 ] );
                [1.048808848, 1.788854382, 2.387467277]

> map( x -> x + 1, { 1, 3, 5 } );
                               {2, 4, 6}

> sqrt~( [ 1.1, 3.2, 5.7 ] );
                [1.048808848, 1.788854382, 2.387467277]

> (x -> x + 1)~( { 1, 3, 5 } );
                               {2, 4, 6}

For Arrays (Vectors, Matrices, etc.) both map and trailing tilde also work, and by default create a new object, leaving the input Array unchanged.

> a := Array( [ 1.1, 3.2, 5.7 ] );
                          a := [1.1, 3.2, 5.7]

> sqrt~( a );
                [1.048808848, 1.788854382, 2.387467277]

> a;
                            [1.1, 3.2, 5.7]

> map( sqrt, a );
                [1.048808848, 1.788854382, 2.387467277]

> a;
                            [1.1, 3.2, 5.7]

However, since these are mutable data structures in Maple, it is possible to use map to modify its input according to the applied procedure.

> map[inplace]( sqrt, a );
                [1.048808848, 1.788854382, 2.387467277]

> a;
                [1.048808848, 1.788854382, 2.387467277]

The Array a has been modified.

It is also possible to pass additional arguments to the mapped procedure.

> map( `+`, [ 1, 2, 3 ], 3 );
                               [4, 5, 6]

Passing additional arguments *before* the arguments from the mapped data structure is achieved using map2, or the more general map[n] procedure.

> map2( `-`, 5, [ 1, 2, 3 ] );
                               [4, 3, 2]

> map[2]( `/`, 5, [ 1, 2, 3 ] );
                             [5, 5/2, 5/3]

Mathematica//Wolfram Language

(#*#)& /@ {1, 2, 3, 4}
Map[Function[#*#], {1, 2, 3, 4}]
Map[((#*#)&,{1,2,3,4}]
Map[Function[w,w*w],{1,2,3,4}]

MATLAB

There are two types of arrays in MATLAB: arrays and cell arrays. MATLAB includes two functions, one for each of these data types, that accomplish the specification for this task. For arrays, we use "arrayfun()"; for cell arrays we use "cellfun()".
Example: For both of these function the first argument is a function handle for the function we would like to apply to each element. The second argument is the array whose elements are modified by the function. The function can be any function, including user defined functions.

>> array = [1 2 3 4 5]

array =

     1     2     3     4     5

>> arrayfun(@sin,array)

ans =

  Columns 1 through 4

   0.841470984807897   0.909297426825682   0.141120008059867  -0.756802495307928

  Column 5

  -0.958924274663138

>> cellarray = {1,2,3,4,5}

cellarray = 

    [1]    [2]    [3]    [4]    [5]

>> cellfun(@tan,cellarray)

ans =

  Columns 1 through 4

   1.557407724654902  -2.185039863261519  -0.142546543074278   1.157821282349578

  Column 5

  -3.380515006246586

Maxima

/* for lists or sets */

map(sin, [1, 2, 3, 4]);
map(sin, {1, 2, 3, 4});

/* for matrices */

matrixmap(sin, matrix([1, 2], [2, 4]));

min

Works with: min version 0.19.3

(1 2 3 4 5) (sqrt puts) foreach   ; print each square root
(1 2 3 4 5) 'sqrt map             ; collect return values

Modula-3

MODULE Callback EXPORTS Main;

IMPORT IO, Fmt;

TYPE CallBack = PROCEDURE (a: CARDINAL; b: INTEGER);
     Values = REF ARRAY OF INTEGER;

VAR sample := ARRAY [1..5] OF INTEGER {5, 4, 3, 2, 1};
    callback := Display;

PROCEDURE Display(loc: CARDINAL; val: INTEGER) =
  BEGIN
    IO.Put("array[" & Fmt.Int(loc) & "] = " & Fmt.Int(val * val) & "\n");
  END Display;

PROCEDURE Map(VAR values: ARRAY OF INTEGER; size: CARDINAL; worker: CallBack) =
  VAR lvalues := NEW(Values, size);
  BEGIN
    FOR i := FIRST(lvalues^) TO LAST(lvalues^) DO
      worker(i, values[i]);
    END;
  END Map;

BEGIN
  Map(sample, NUMBER(sample), callback);
END Callback.

Nanoquery

// create a list of numbers 1-10
numbers = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
 
// display the list as it is
println numbers
 
// square each element in the list
for i in range(1, len(numbers) - 1)
	numbers[i] = numbers[i] * numbers[i]
end
 
// display the squared list
println numbers

Output:

[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]

Nemerle

The Nemerle.Collections namespace defines the methods Iter() (if the function applied is void) and Map() (if the function applied returns a value).

def seg = array[1, 2, 3, 5, 8, 13];
def squares = seq.Map(x => x*x);

NetLogo

;; NetLogo “anonymous procedures”
;; stored in a variable, just to show it can be done.
let callback [ [ x ] x * x ]
show (map callback [ 1 2 3 4 5 ])

NewLISP

> (map (fn (x) (* x x)) '(1 2 3 4))
(1 4 9 16)

NGS

{
	[1, 2, 3, 4, 5].map(F(x) x*x)
}

Nial

each (* [first, first] ) 1 2 3 4
=1 4 9 16

Nim

from std/sequtils import apply
let arr = @[1,2,3,4]
arr.apply proc(some: int) = echo(some, " squared = ", some*some)

Output:

 1 squared = 1
 2 squared = 4
 3 squared = 9
 4 squared = 16

Nutt

module main
imports native.io.output.say

operator |> (arr:Array,f:Procedure):Array==>{f(x) of x |-> arr}

say({0,1,2,3,4,5}|>a==>a+2)//|{2,3,4,5,6,7}

end

Oberon-2

Works with: oo2x

MODULE ApplyCallBack;
IMPORT
  Out := NPCT:Console;

TYPE
  Fun = PROCEDURE (x: LONGINT): LONGINT;
  Ptr2Ary = POINTER TO ARRAY OF LONGINT;

VAR
  a: ARRAY 5 OF LONGINT;
  x: ARRAY 3 OF LONGINT;
  r: Ptr2Ary;

  PROCEDURE Min(x,y: LONGINT): LONGINT;
  BEGIN
    IF x <= y THEN RETURN x ELSE RETURN y END;
  END Min;

  PROCEDURE Init(VAR a: ARRAY OF LONGINT);
  BEGIN
    a[0] := 0;
    a[1] := 1;
    a[2] := 2;
    a[3] := 3;
    a[4] := 4;
  END Init;

  PROCEDURE Fun1(x: LONGINT): LONGINT;
  BEGIN
    RETURN x * 2
  END Fun1;

  PROCEDURE Fun2(x: LONGINT): LONGINT;
  BEGIN
    RETURN x DIV 2;
  END Fun2;

  PROCEDURE Fun3(x: LONGINT): LONGINT;
  BEGIN
    RETURN x + 3;
  END Fun3;
  
  PROCEDURE Map(F: Fun; VAR x: ARRAY OF LONGINT);
  VAR
    i: LONGINT;
  BEGIN 
    FOR i := 0 TO LEN(x) - 1 DO
      x[i] := F(x[i])
    END
  END Map;

  PROCEDURE Map2(F: Fun; a: ARRAY OF LONGINT; VAR r: ARRAY OF LONGINT);
  VAR
    i,l: LONGINT;
  BEGIN
    l := Min(LEN(a),LEN(x));
    FOR i := 0 TO l - 1 DO 
      r[i] := F(a[i])
    END
  END Map2;

  PROCEDURE Map3(F: Fun; a: ARRAY OF LONGINT): Ptr2Ary;
  VAR
    r: Ptr2Ary;
    i: LONGINT;
  BEGIN
    NEW(r,LEN(a));
    FOR i := 0 TO LEN(a) - 1 DO
      r[i] := F(a[i]);
    END;
    RETURN r
  END Map3;

  PROCEDURE Show(a: ARRAY OF LONGINT);
  VAR
    i: LONGINT;
  BEGIN
    FOR i := 0 TO LEN(a) - 1 DO
      Out.Int(a[i],4)
    END;
    Out.Ln
  END Show;
  
BEGIN
  Init(a);Map(Fun1,a);Show(a);
  Init(a);Map2(Fun2,a,x);Show(x);
  Init(a);r := Map3(Fun3,a);Show(r^);
END ApplyCallBack.

Output:

   0   2   4   6   8
   0   0   1
   3   4   5   6   7

Objeck

use Structure;

bundle Default {
  class Test {
    function : Main(args : String[]) ~ Nil {
      Run();
    }

    function : native : Run() ~ Nil {
      values := IntVector->New([1, 2, 3, 4, 5]);
      squares := values->Apply(Square(Int) ~ Int);
      each(i : squares) {
        squares->Get(i)->PrintLine();
      };
    }
    
    function : Square(value : Int) ~ Int {
      return value * value;
    }
  }
}

OCaml

This function is part of the standard library:

Array.map

Usage example:

let square x = x * x;;
let values = Array.init 10 ((+) 1);;
Array.map square values;;

Or with lists (which are more typical in OCaml):

let values = [1;2;3;4;5;6;7;8;9;10];;
List.map square values;;

Use iter if the applied function does not return a value.

Array.iter (fun x -> Printf.printf "%d" x) [|1; 2; 3; 4; 5|];;

List.iter (fun x -> Printf.printf "%d" x) [1; 2; 3; 4; 5];;

with partial application we can also write:

Array.iter (Printf.printf "%d") [|1; 2; 3; 4; 5|];;

List.iter (Printf.printf "%d") [1; 2; 3; 4; 5];;

Octave

Almost all the built-in can operate on each element of a vector or matrix; e.g. sin([pi/2, pi, 2*pi]) computes the function sin on pi/2, pi and 2*pi (returning a vector). If a function does not accept vectors/matrices as arguments, the arrayfun can be used.

function e = f(x, y)
  e = x^2 + exp(-1/(y+1));
endfunction

% f([2,3], [1,4]) gives and error, but
arrayfun(@f, [2, 3], [1,4])
% works

(The function f can be rewritten so that it can accept vectors as argument simply changing operators to their dot relatives: e = x.^2 + exp(-1 ./ (y.+1)))

Odin

package main

import "core:slice"
import "core:fmt"

squared :: proc(x: int) -> int {
  return x * x
}

main :: proc() {
  arr := []int{1, 2, 3, 4, 5}
  res := slice.mapper(arr, squared)

  fmt.println(res)  // prints: [1, 4, 9, 16, 25]
}

Oforth

apply allows to perform a function on all elements of a list :

0 #+ [ 1, 2, 3, 4, 5 ] apply

map regroups all results into a new list :

#sq [ 1, 2, 3, 4, 5 ] map

Ol

Apply custom callback (lambda) to every element of list.

(for-each
   (lambda (element)
      (display element))
   '(1 2 3 4 5))
; ==> 12345

ooRexx

ooRexx doesn't directly support callbacks on array items, but this is pretty easy to implement using Routine objects.

start = .array~of("Rick", "Mike", "David", "Mark")
new = map(start, .routines~reversit)
call map new, .routines~sayit


-- a function to perform an iterated callback over an array
-- using the provided function.  Returns an array containing
-- each function result
::routine map
  use strict arg array, function
  resultArray = .array~new(array~items)
  do item over array
     resultArray~append(function~call(item))
  end
  return resultArray

::routine reversit
  use arg string
  return string~reverse

::routine sayit
  use arg string
  say string
  return .true   -- called as a function, so a result is required

Output:

kciR
ekiM
divaD
kraM

Order

Both sequences and tuples support the usual map operation seen in many functional languages. Sequences also support 8seq_for_each, and a few variations, which returns 8nil.

#include <order/interpreter.h>

ORDER_PP( 8tuple_map(8fn(8X, 8times(8X, 8X)), 8tuple(1, 2, 3, 4, 5)) )
// -> (1,4,9,16,25)

ORDER_PP( 8seq_map(8fn(8X, 8times(8X, 8X)), 8seq(1, 2, 3, 4, 5)) )
// -> (1)(4)(9)(16)(25)

ORDER_PP( 8seq_for_each(8fn(8X, 8print(8X 8comma)), 8seq(1, 2, 3, 4, 5)) )
// prints 1,2,3,4,5, and returns 8nil

Oz

declare
  fun{Square A}
    A*A
  end

  Lst = [1 2 3 4 5]
  
  %% apply a PROCEDURE to every element
  {ForAll Lst Show}

  %% apply a FUNCTION to every element
  Result = {Map Lst Square}
  {Show Result}

PARI/GP

Works with: PARI/GP version 2.4.2 and above

callback(n)=n+n;
apply(callback, [1,2,3,4,5])

This should be contrasted with call:

call(callback, [1,2,3,4,5])

which is equivalent to callback(1, 2, 3, 4, 5) rather than [callback(1), callback(2), callback(3), callback(4), callback(5)].

Pascal

See Delphi

Perl

# create array
my @a = (1, 2, 3, 4, 5);

# create callback function
sub mycallback {
  return 2 * shift;
}

# use array indexing
for (my $i = 0; $i < scalar @a; $i++) {
  print "mycallback($a[$i]) = ", mycallback($a[$i]), "\n";
}

# using foreach
foreach my $x (@a) {
  print "mycallback($x) = ", mycallback($x), "\n";
}

# using map (useful for transforming an array)
my @b = map mycallback($_), @a;                # @b is now (2, 4, 6, 8, 10)

# and the same using an anonymous function
my @c = map { $_ * 2 } @a;                     # @c is now (2, 4, 6, 8, 10)

# use a callback stored in a variable
my $func = \&mycallback;
my @d = map $func->($_), @a;                  # @d is now (2, 4, 6, 8, 10)

# filter an array 
my @e = grep { $_ % 2 == 0 } @a;               # @e is now (2, 4)

Phix

Library: Phix/basics

requires("0.8.2")
 
function add1(integer x)
    return x + 1
end function
 
?apply({1,2,3},add1)

Output:

{2,3,4}

There are in fact three ways to invoke apply:
The oldest/original, as above, is apply(s,fn), where fn is invoked length(s) times with a single parameter of s[i].
apply(false,fn,s) likewise invokes fn length(s) times, but each time with length(s[i]) parameters.
apply(true,sprintf,{{"%d"},s}), the third way, invokes sprintf length(s) times with two parameters, being "%d" and each s[i].
This last way scans it's third argument looking for a (consistent) longest length to determine how many times to invoke sprintf,
uses the length of it's third argument to determine how many parameters each call will get, and
uses the same value on every call for any atom or length 1 elements, such as that {"%d"}.

Phixmonti

/# Rosetta Code problem: http://rosettacode.org/wiki/Apply_a_callback_to_an_array
by Galileo, 05/2022 #/

include ..\Utilitys.pmt

def ++
    1 +
enddef

def square
    dup *
enddef

( 1 2 3 ) dup

getid ++ map swap
getid square map

pstack

Output:

[[2, 3, 4], [1, 4, 9]]

=== Press any key to exit ===

PHP

function cube($n)
{
   return($n * $n * $n);
}

$a = array(1, 2, 3, 4, 5);
$b = array_map("cube", $a);
print_r($b);

Picat

Picat doesn't support anonymous (lambda) functions so the function must be defined in the program to be used by - say - map/2. There are - however - quite a few ways without proper lambdas, using map/2, apply/2, or list comprehensions.

go => 
   L = 1..10,

   % Using map/2 in different ways
   println(L.map(fun)), 
   println(map(L,fun)),   
   println(map(fun,L)),

   % List comprehensions
   println([fun(I) : I in L]),

   % Using apply/2
   println([apply(fun,I) : I in L]),

   % And using list comprehension with the function directly.
   println([I*I : I in L]),
   nl.

% Some function
fun(X) = X*X.

Translation of: Prolog

This variant is inspired by the Prolog solution (using assert/1 to define a predicate) and shows the integration with Picat's underlying B-Prolog engine.

Picat does not support assert/1 directly, so one have to do the assert/1 in the bp module space (the module/space for the B-Prolog engine). To call the defined predicate, one must prepend the predicate name with "bp.".

Note that fun2/2 is not a function so map/2 or apply/2 cannot be used here.

go2 =>
   L = 1..10,

   % Define the predicate _in the bp space_.
   bp.assert( $(fun2(X,Y) :- Y is X*X) ),

   % Use bp.fun2 to call the function.
   println([B : A in L, bp.fun2(A,B)]),
   nl.

Using this technique one can do quite much "real" Prolog stuff even though Picat doesn't support it directly. However, one should be careful with this approach since it can sometimes be confusing and it doesn't work in all cases.

PicoLisp

: (mapc println (1 2 3 4 5))  # Print numbers
1
2
3
4
5
-> 5

: (mapcar '((N) (* N N)) (1 2 3 4 5))  # Calculate squares
-> (1 4 9 16 25)

: (mapcar ** (1 2 3 4 5) (2 .))  # Same, using a circular list
-> (1 4 9 16 25)

: (mapcar if '(T NIL T NIL) '(1 2 3 4) '(5 6 7 8))  # Conditional function
-> (1 6 3 8)

Pike

int cube(int n)
{
    return n*n*n;
}

array(int) a = ({ 1,2,3,4,5 });
array(int) b = cube(a[*]);      // automap operator
array(int) c = map(a, cube);    // conventional map function

PL/I

   declare x(5) initial (1,3,5,7,8);
   x = sqrt(x);
   x = sin(x);

PL/SQL

PL/SQL doesn't have callbacks, though we can pass around an object and use its method to simulate one. Further, this callback method can be defined in an abstract class that the mapping function will expect.

-- Let's create a generic class with one method to be used as an interface:
create or replace
TYPE callback AS OBJECT (
    -- A class needs at least one member even though we don't use it
    -- There's no generic OBJECT type, so let's call it NUMBER
    dummy NUMBER,
    -- Here's our function, and since PL/SQL doesn't have generics,
    -- let's use type NUMBER for our params
    MEMBER FUNCTION exec(n number) RETURN number
) NOT FINAL not instantiable;
/

-- Now let's inherit from that, defining a class with one method. We'll have ours square a number.
-- We can pass this class into any function that takes type callback:
CREATE OR REPLACE TYPE CB_SQUARE under callback (
    OVERRIDING MEMBER FUNCTION exec(n NUMBER) RETURN NUMBER
)
/
CREATE OR REPLACE
TYPE BODY CB_SQUARE AS
    OVERRIDING MEMBER FUNCTION exec(n NUMBER) RETURN NUMBER IS
    BEGIN
        RETURN n * n;
    END exec;
END;
/

-- And a package to hold our test
CREATE OR REPLACE 
PACKAGE PKG_CALLBACK AS 
    myCallback cb_square;
    TYPE intTable IS TABLE OF NUMBER INDEX BY BINARY_INTEGER;
    ints intTable;
    i PLS_INTEGER;
    
    procedure test_callback;
END PKG_CALLBACK;
/

CREATE OR REPLACE PACKAGE BODY PKG_CALLBACK AS
    -- Our generic mapping function that takes a "method" and a collection
    -- Note that it takes the generic callback type 
    -- that doesn't know anything about squaring
    procedure do_callback(myCallback IN callback, ints IN OUT intTable) IS
        i PLS_INTEGER;
        myInt NUMBER;
    begin
        for i in 1 .. ints.count loop
            myInt := ints(i);
            -- PL/SQL call's the child's method
            ints(i) := myCallback.exec(myInt);
        END LOOP;
    end do_callback;

    procedure test_callback IS
    BEGIN
        myCallback := cb_square(null);
        FOR i IN 1..5 LOOP
            ints(i) := i;
        END LOOP;
    
        do_callback(myCallback, ints);
    
        i := ints.FIRST;
        WHILE i IS NOT NULL LOOP
            DBMS_OUTPUT.put_line(ints(i));
            i := ints.next(i);
        END LOOP;
    END test_callback;
END PKG_CALLBACK;
/

BEGIN
  PKG_CALLBACK.TEST_CALLBACK();
END;
/

Pop11

;;; Define a procedure
define proc(x);
    printf(x*x, '%p,');
enddefine;

;;; Create array
lvars ar = { 1 2 3 4 5};

;;; Apply procedure to array
appdata(ar, proc);

If one wants to create a new array consisting of transformed values then procedure mapdata may be more convenient.

PostScript

The forall operator applies a procedure to each element of an array, a packed array or a string.

[1 2 3 4 5] { dup mul = } forall

In this case the respective square numbers for the elements are printed.

To create a new array from the results above code can simply be wrapped in []:

[ [1 2 3 4 5] { dup mul } forall ]

Library: initlib

[1 2 3 4 5] {dup *} map

PowerShell

This can be done in PowerShell with the ForEach-Object cmdlet which applies a scriptblock to each element of an array:

1..5 | ForEach-Object { $_ * $_ }

To recreate a map function, found in other languages the same method applies:

function map ([array] $a, [scriptblock] $s) {
    $a | ForEach-Object $s
}
map (1..5) { $_ * $_ }

Prolog

Prolog doesn't have arrays, but we can do it with lists. This can be done in the console mode.

 ?- assert((fun(X, Y) :- Y is 2 * X)).
true.

?- maplist(fun, [1,2,3,4,5], L).
L = [2,4,6,8,10].

PureBasic

Procedure Cube(Array param.i(1))
    Protected n.i
    For n = 0 To ArraySize(param())
        Debug Str(param(n)) + "^3 = " + Str(param(n) * param(n) * param(n))
    Next 
EndProcedure 

Dim AnArray.i(4)

For n = 0 To ArraySize(AnArray()) 
    AnArray(n) = Random(99)
Next 

Cube(AnArray())

Python

def square(n):
    return n * n
  
numbers = [1, 3, 5, 7]

squares1 = [square(n) for n in numbers]     # list comprehension

squares2a = map(square, numbers)            # functional form

squares2b = map(lambda x: x*x, numbers)     # functional form with `lambda`

squares3 = [n * n for n in numbers]         # no need for a function,
                                            # anonymous or otherwise

isquares1 = (n * n for n in numbers)        # iterator, lazy

import itertools
isquares2 = itertools.imap(square, numbers) # iterator, lazy

To print squares of integers in the range from 0 to 9, type:

print " ".join(str(n * n) for n in range(10))

Or:

print " ".join(map(str, map(square, range(10))))

Result:

0 1 4 9 16 25 36 49 64 81

QB64

'Task
'Take a combined set of elements and apply a function to each element.
'UDT
Type Friend
    Names As String * 8
    Surnames As String * 8
    Age As Integer
End Type

Dim Friends(1 To 6) As Friend
Restore
FillArray
SearchForAdult Friends(), LBound(friends), UBound(friends)

End

Data "John","Beoz",13,"Will","Strange",22
Data "Arthur","Boile",16,"Peter","Smith",21
Data "Tom","Parker",14,"Tim","Wesson",24

Sub FillArray
    Shared Friends() As Friend
    Dim indeX As Integer
    For indeX = LBound(friends) To UBound(friends) Step 1
        Read Friends(indeX).Names, Friends(indeX).Surnames, Friends(indeX).Age
    Next
End Sub

Sub SearchForAdult (F() As Friend, Min As Integer, Max As Integer)
    Dim Index As Integer
    Print "Friends with more than 18 years old"
    For Index = Min To Max Step 1
        If F(Index).Age > 18 Then Print F(Index).Names; " "; F(Index).Surnames; " "; F(Index).Age
    Next Index
End Sub

Quackery

As a dialogue in the Quackery shell (REPL), applying the word cubed to the nest [ 1 2 3 4 5 6 7 8 9 10 ], first treating the nest as a list, then as an array.

/O> [ 3 ** ] is cubed ( n --> n )
... 

Stack empty.

/O> ' [ 1 2 3 4 5 6 7 8 9 10 ]
... [] swap witheach 
...   [ cubed join ]
... 

Stack: [ 1 8 27 64 125 216 343 512 729 1000 ] 

/O> drop
... 

Stack empty.

/O> ' [ 1 2 3 4 5 6 7 8 9 10 ]
... dup witheach
...   [ cubed swap i^ poke ]
... 

Stack: [ 1 8 27 64 125 216 343 512 729 1000 ]

R

Many functions can take advantage of implicit vectorisation, e.g.

cube <- function(x) x*x*x
elements <- 1:5
cubes <- cube(elements)

Explicit looping over array elements is also possible.

cubes <- numeric(5)
for(i in seq_along(cubes))
{
   cubes[i] <- cube(elements[i])
}

Loop syntax can often simplified using the *apply family of functions.

elements2 <- list(1,2,3,4,5)
cubes <- sapply(elements2, cube)

In each case above, the value of 'cubes' is

1   8  27  64 125

Racket

#lang racket

;; using the `for/vector' comprehension form
(for/vector ([i #(1 2 3 4 5)]) (sqr i))

;; the usual functional `map'
(vector-map sqr #(1 2 3 4 5))

Raku

(formerly Perl 6)

Works with: Rakudo version 2015.10-11

sub function { 2 * $^x + 3 };
my @array = 1 .. 5;

# via map function
.say for map &function, @array;

# via map method
.say for @array.map(&function);

# via for loop
for @array {
    say function($_);
}

# via the "hyper" metaoperator and method indirection
say @array».&function;

# we neither need a variable for the array nor for the function
say [1,2,3]>>.&({ $^x + 1});

Raven

# To print the squared elements
[1 2 3 4 5] each dup * print

# To obtain a new array
group [1 2 3 4 5] each
  dup *
list

REBOL

REBOL [
    Title: "Array Callback"
    URL: http://rosettacode.org/wiki/Apply_a_callback_to_an_Array
]

map: func [
	"Apply a function across an array."
	f [native! function!] "Function to apply to each element of array."
	a [block!] "Array to process."
	/local x
][x: copy []  forall a [append x do [f a/1]]  x]

square: func [x][x * x]

; Tests:

assert: func [code][print [either do code ["  ok"]["FAIL"]  mold code]]

print "Simple loop, modify in place:"
assert [[1 100 81] = (a: [1 10 9]  forall a [a/1: square a/1]  a)]

print [crlf "Functional style with 'map':"]
assert [[4 16 36] = map :square [2 4 6]]

print [crlf "Applying native function with 'map':"]
assert [[2 4 6] = map :square-root [4 16 36]]

Output:

Simple loop, modify in place:
  ok [[1 100 81] = (a: [1 100 81] forall a [a/1: square a/1] a)]

Functional style with 'map':
  ok [[4 16 36] = map :square [2 4 6]]

Applying native function with 'map':
  ok [[2 4 6] = map :square-root [4 16 36]]

Retro

Retro provides a variety of array words. Using these to multiply each value in an array by 10 and display the results:

{ #1 #2 #3 #4 #5 } [ #10 * ] a:map [ n:put sp ] a:for-each

REXX

/*REXX program applies a  callback  to an array  (using factorials for a demonstration).*/
numeric digits 100                               /*be able to display some huge numbers.*/
parse arg # .                                    /*obtain an optional value from the CL.*/
a.=                                              /*initialize the array  A  to all nulls*/
if #=='' | #==","  then #= 12                    /*Not assigned?  Then use default value*/
                        do j=0  to #;   a.j= j   /*assign the integer   J  ───►   A.j   */
                        end   /*j*/              /*array  A  will have N values: 0 ──► #*/

call listA   'before callback'                   /*display  A  array before the callback*/
say                                              /*display a blank line for readability.*/
say '      ··· applying callback to array A ···' /*display what is about to happen to B.*/
say                                              /*display a blank line for readability.*/
call bangit  'a'                                 /*factorialize (the values) of A array.*/
                                                 /*    store the results  ───►  array B.*/
call listA   ' after callback'                   /*display  A  array after the callback.*/
exit 0                                           /*stick a fork in it,  we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
bangit:   do v=0;  $= value(arg(1)'.'v);  if $=='' then return  /*No value?  Then return*/
          call value arg(1)'.'v, fact($)         /*assign a value (a factorial) to array*/
          end    /*i*/
/*──────────────────────────────────────────────────────────────────────────────────────*/
fact:   procedure; arg x;   != 1;         do f=2  to x;  != !*f;  end; /*f*/;     return !
listA:    do k=0  while a.k\=='';  say arg(1)  'a.'k"="  a.k;     end  /*k*/;     return

output when using the default input:

before callback a.0= 0
before callback a.1= 1
before callback a.2= 2
before callback a.3= 3
before callback a.4= 4
before callback a.5= 5
before callback a.6= 6
before callback a.7= 7
before callback a.8= 8
before callback a.9= 9
before callback a.10= 10
before callback a.11= 11
before callback a.12= 12

      ··· applying callback to array A ···

 after callback a.0= 1
 after callback a.1= 1
 after callback a.2= 2
 after callback a.3= 6
 after callback a.4= 24
 after callback a.5= 120
 after callback a.6= 720
 after callback a.7= 5040
 after callback a.8= 40320
 after callback a.9= 362880
 after callback a.10= 3628800
 after callback a.11= 39916800
 after callback a.12= 479001600

Ring

for x in [1,2,3,4,5]
    x = x*x
next

RLaB

RLaB has two type of arrays: 'standard' or 1-dimensional, that can be a row- or a column-vectory; and, 'associative' which are called lists. For standard array its entry identifier (index) is an integer in range 1:N where N is the size of the array. For associative array its entry identifier is a string consisting of printable ASCII characters.

All scalar mathematical functions are 'matrix-optimized' meaning that if the argument to a function is a matrix, then the return value of the function is a matrix of the same size as the input argument, where the function is applied to the individual entries of the matrix. Consider an example:

>> x = rand(2,4)
 0.707213207   0.275298961   0.396757763   0.232312312
 0.215619868   0.207078017   0.565700032   0.666090571
>> sin(x)
 0.649717845   0.271834652   0.386430003   0.230228332
 0.213952984   0.205601224   0.536006923   0.617916954

This can be done on entry-by-entry basis, but one has to keep in mind that the 'for' or 'while' loops are slow in interpreted languages, and RLaB is no exception.

x = rand(2,4);
y = zeros(2,4);
for (i in 1:2)
{
  for (j in 1:4)
  {
    y[i;j] = sin( x[i;j] );
  }
}

The functions can take lists as arguments, but then it has to be specified within the body of the function what to do with the list elements. Given a list call it 'x' there is a RLaB function 'members' which returns a string vector with the names of the elements of the list.

x = <<>>;
for (i in 1:9)
{
  x.[i] = rand();
}

y = <<>>;
for (i in members(x))
{
  y.[i] = sin( x.[i] );
}

RPL

Works with: Halcyon Calc version 4.2.7

≪ → array func 
  ≪ array 0 CON 
     1 array SIZE FOR j 
        j array j GET func EVAL PUT 
     NEXT 
≫  ≫ 
´MAP’ STO

[1,2,3,4,5,6,7,8,9] ≪ SQ ≫ MAP

Output:

1: [ 1 4 9 16 25 36 49 64 81 ]

Ruby

You could use a traditional "for i in arr" approach like below:

for i in [1,2,3,4,5] do
   puts i**2
end

Or you could the more preferred ruby way of an iterator (which is borrowed from SmallTalk)

[1,2,3,4,5].each{ |i| puts i**2 }

To create a new array of each value squared

[1,2,3,4,5].map{ |i| i**2 }

Rust

fn echo(n: &i32) {
    println!("{}", n);
}

fn main() {
    let a: [i32; 5];
    a = [1, 2, 3, 4, 5];
    let _: Vec<_> = a.into_iter().map(echo).collect();
}

Salmon

These examples apply the square function to a list of the numbers from 0 through 9 to produce a new list of their squares, then iterate over the resulting list and print the squares.

function apply(list, ageless to_apply)
  (comprehend(x; list) (to_apply(x)));

function square(x) (x*x);

iterate(x; apply([0...9], square))
    x!;

With short identifiers:

include "short.salm";

fun apply(list, ageless to_apply)
  (comp(x; list) (to_apply(x)));

fun square(x) (x*x);

iter(x; apply([0...9], square))
    x!;

With the numbers given as a list of individual elements:

function apply(list, to_apply)
  (comprehend(x; list) (to_apply(x)));

function square(x) (x*x);

iterate(x; apply([0, 1, 2, 3, 4, 5, 6, 7, 8, 9], square))
    x!;

Sather

class MAIN is
  do_something(i:INT):INT is
    return i * i;
  end;

  main is
    a:ARRAY{INT} := |1, 2, 3, 4, 5|;
    -- we use an anonymous closure to apply our do_something "callback"
    a.map(bind(do_something(_)));
    loop #OUT + a.elt! + "\n"; end;
  end;
end;

Scala

val l = List(1,2,3,4)
l.foreach {i => println(i)}

When the argument appears only once -as here, i appears only one in println(i) - it may be shortened to

l.foreach(println(_))

Same for an array

val a = Array(1,2,3,4)
a.foreach {i => println(i)}
a.foreach(println(_))  '' // same as previous line''

Or for an externally defined function:

def doSomething(in: int) = {println("Doing something with "+in)}
l.foreach(doSomething)

There is also a for syntax, which is internally rewritten to call foreach. A foreach method must be defined on a

for(val i <- a) println(i)

It is also possible to apply a function on each item of an list to get a new list (same on array and most collections)

val squares = l.map{i => i * i} ''//squares is''  List(1,4,9,16)

Or the equivalent for syntax, with the additional keyword yield, map is called instead of foreach

val squares = for (val i <- l) yield i * i

Scheme

(define (square n) (* n n))
(define x #(1 2 3 4 5))
(map square (vector->list x))

A single-line variation

(map (lambda (n) (* n n)) '(1 2 3 4 5))

For completeness, the map function (which is R5RS standard) can be coded as follows:

(define (map f L)
  (if (null? L)
      L
      (cons (f (car L)) (map f (cdr L)))))

SenseTalk

put each item in [1,2,3,5,9,14,24] squared

put myFunc of each for each item of [1,2,3,5,9,14,24]

to handle myFunc of num
	return 2*num + 1
end myFunc

Output:

(1,4,9,25,81,196,576)
(3,5,7,11,19,29,49)

Sidef

Defining a callback function:

func callback(i) { say i**2 }

The function will get called for each element:

[1,2,3,4].each(callback)

Same as above, but with the function inlined:

[1,2,3,4].each{|i| say i**2 }

For creating a new array, we can use the Array.map method:

[1,2,3,4,5].map{|i| i**2 }

Simula

BEGIN

    ! APPLIES A CALLBACK FUNCTION TO AN ARRAY ;
    PROCEDURE APPLY(ARR, FUN);
        REAL ARRAY ARR;
        PROCEDURE FUN IS REAL PROCEDURE FUN(X); REAL X;;
    BEGIN
        INTEGER I;
        FOR I := LOWERBOUND(ARR, 1) STEP 1 UNTIL UPPERBOUND(ARR, 1) DO
            ARR(I) := FUN(ARR(I));
    END APPLY;

    ! CALLBACK ;
    REAL PROCEDURE SQUARE(X); REAL X; SQUARE := X * X;

    REAL ARRAY A(1:5);
    INTEGER I;
    FOR I := 1 STEP 1 UNTIL 5 DO A(I) := I;
    APPLY(A, SQUARE);
    FOR I := 1 STEP 1 UNTIL 5 DO OUTFIX(A(I), 2, 8); OUTIMAGE;

END.

Output:

    1.00    4.00    9.00   16.00   25.00

Slate

#( 1 2 3 4 5 ) collect: [| :n | n * n].

Smalltalk

#( 1 2.0 'three') do: [:each | each displayNl].

You can tell symbols how to react to the value: message, and then write ²:

#( 1 2.0 'three') do: #displayNl.

2) actually most dialects already have it, and it is trivial to add, if it does not.

There is a huge number of additional enumeration messages implemented in Collection, from which Array inherits. Eg.:

#( 1 2 3 4 5 ) collect: [:n | n * n].

Sparkling

The foreach function calls the supplied callback on each element of the (possibly associative) array, passing it each key and the corresponding value:

let numbers = { 1, 2, 3, 4 };
foreach(numbers, function(idx, num) {
    print(num);
});

The map function applies the transform to each key-value pair and constructs a new array, of which the keys are the keys of the original array, and the corresponding values are the return values of each call to the transform function:

let dict = { "foo": 42, "bar": 13, "baz": 37 };
let doubled = map(dict, function(key, val) {
    return val * 2;
});

SQL PL

Works with: Db2 LUW

version 9.7 or higher.

With SQL PL:

--#SET TERMINATOR @

SET SERVEROUTPUT ON @

BEGIN
 DECLARE TYPE NUMBERS AS SMALLINT ARRAY[5];
 DECLARE NUMBERS NUMBERS;
 DECLARE I SMALLINT;

 SET I = 1;
 WHILE (I <= 5) DO
  SET NUMBERS[I] = I;
  SET I = I + 1;
 END WHILE;

 BEGIN
  DECLARE PROCEDURE PRINT_SQUARE (
    IN VALUE SMALLINT
   )
  BEGIN
   CALL DBMS_OUTPUT.PUT(VALUE * VALUE || ' ');
  END;

  SET I = 1;
  WHILE (I <= 5) DO
   CALL PRINT_SQUARE(NUMBERS[I]);
   SET I = I + 1;
  END WHILE;
  CALL DBMS_OUTPUT.PUT_LINE('');
 END;
END @

Output:

db2 -td@
db2 => BEGIN
...
db2 (cont.) => END @
DB20000I  The SQL command completed successfully.

1 4 9 16 25

Standard ML

map f l

i.e.

map (fn x=>x+1) [1,2,3];; (* [2,3,4] *)

Stata

There is no 'map' function in Mata, but it's easy to implement. Notice that you can only pass functions that are written in Mata, no builtin ones. For instance, the trigonometric functions (cos, sin) or the exponential are builtin. To pass a builtin function to another function, one needs to write a wrapper in Mata. See also Stata help about pointers and passing functions to functions. There are two versions of the function: one to return a numeric array, another to return a string array.

function map(f,a) {
	nr = rows(a)
	nc = cols(a)
	b = J(nr,nc,.)
	for (i=1;i<=nr;i++) {
		for (j=1;j<=nc;j++) b[i,j] = (*f)(a[i,j])
	}
	return(b)
}

function maps(f,a) {
	nr = rows(a)
	nc = cols(a)
	b = J(nr,nc,"")
	for (i=1;i<=nr;i++) {
		for (j=1;j<=nc;j++) b[i,j] = (*f)(a[i,j])
	}
	return(b)
}

function square(x) {
	return(x*x)
}

Output

: map(&square(),(1,2,3\4,5,6))
        1    2    3
    +----------------+
  1 |   1    4    9  |
  2 |  16   25   36  |
    +----------------+

SuperCollider

Actually, there is a builtin squared operator:

[1, 2, 3].squared  // returns [1, 4, 9]

Anything that is a Collection can be used with collect:

[1, 2, 3].collect { |x| x * x }

List comprehension combined with a higher-order function can also be used:

var square = { |x| x * x };
var map = { |fn, xs|
  all {: fn.value(x), x <- xs };
};
map.value(square, [1, 2, 3]);

Swift

func square(n: Int) -> Int {
    return n * n
}

let numbers = [1, 3, 5, 7]

let squares1a = numbers.map(square)         // map method on array

let squares1b = numbers.map {x in x*x}      // map method on array with anonymous function

let squares1b = numbers.map { $0 * $0 }      // map method on array with anonymous function and unnamed parameters

let isquares1 = numbers.lazy.map(square)   // lazy sequence

Tailspin

def numbers: [1,3,7,10];

templates cube
  $ * $ * $ !
end cube

// Using inline array templates (which also allows access to index by $i)
$numbers -> \[i]($ * $i !\) -> !OUT::write
$numbers -> \[i]($ * $ !\) -> !OUT::write
$numbers -> \[i]($ -> cube !\) -> !OUT::write

// Using array literal and deconstructor
[ $numbers... -> $ * $ ] -> !OUT::write
[ $numbers... -> cube ] -> !OUT::write

Tcl

If I wanted to call "myfunc" on each element of dat and dat were a list:

foreach var $dat {
    myfunc $var
}

This does not retain any of the values returned by myfunc.

if dat were an (associative) array, however:

foreach name [array names dat] {
    myfunc $dat($name)
}

More functional, with a simple map function:

proc map {f list} {
   set res {}
   foreach e $list {lappend res [$f $e]}
   return $res
}
proc square x {expr {$x*$x}}

% map square {1 2 3 4 5}
1 4 9 16 25

TI-89 BASIC

© For no return value
Define foreach(fe_cname,fe_list) = Prgm
  Local fe_i
  For fe_i,1,dim(fe_list)
    #fe_cname(fe_list[fe_i])
  EndFor
EndPrgm

© For a list of results
Define map(map_cnam,map_list) = seq(#map_cnam(map_list[map_i]),map_i,1,dim(map_list))

Define callback(elem) = Prgm
  Disp elem
EndPrgm

foreach("callback", {1,2,3,4,5})
Disp map("√", {1,2,3,4,5})

Output:

$1$
$2$
$3$
$4$
$5$
${\begin{Bmatrix}1&{\sqrt {2}}&{\sqrt {3}}&2&{\sqrt {5}}\end{Bmatrix}}$

TIScript

JavaScript alike:

var a = [1, 2, 3, 4, 5];
a.map(function(v) { return v * v; })

Using short form of lambda notation:

var a = [1, 2, 3, 4, 5];
a.map( :v: v*v );

Toka

( array count function -- )
{
  value| array fn |
  [ i array ] is I
  [ to fn swap to array 0 swap [ I array.get :stack fn invoke I array.put ] countedLoop ]
} is map-array

( Build an array )
5 cells is-array a
10 0 a array.put
11 1 a array.put
12 2 a array.put
13 3 a array.put
14 4 a array.put

( Add 1 to each item in the array )
a 5  [ 1 + ] map-array

TorqueScript

--Elm 03:41, 18 June 2012 (UTC)

Callbacks:

function map(%array,%arrayCount,%function)
{
	for(%i=0;%i<%arrayCount;%i++)
	{
		eval("%a = "@%array@"["@%i@"];");
		eval(""@%function@"("@%a@");");
	}
}

Now to set up an array:

$array[0] = "Hello.";
$array[1] = "Hi.";
$array[2] = "How are you?";

Now to call the function correctly:

map("$array",3,"echo");

Which should result in:

=> Hello.

=> Hi.

=> How are you?

TXR

Print 1 through 10 out of a vector, using prinl the callback, right from the system shell command prompt:

$ txr -e '[mapdo prinl #(1 2 3 4 5 6 7 8 9 10)]'
1
2
3
4
5
6
7
8
9
10

mapdo is like mapcar but doesn't accumulate a list, suitable for imperative programming situations when the function is invoked to perform a side effect.

TXR extends Lisp list processing primitives to work with vectors and strings also, which is why mapdo cheerfully traverses a vector.

uBasic/4tH

We cannot transfer the array address, since uBasic/4tH has only got one, but we can transfer the function pointer and size.

S = 5                                  ' Size of the array

For x = 0 To S - 1                     ' Initialize array
  @(x) = x + 1
Next

Proc _MapArray (_SquareRoot, S)        ' Call mapping procedure

For x = 0 To S - 1                     ' Print results
  Print "SQRT(";x+1;") = ";Using "#.####";@(x)
Next

For x = 0 To S - 1                     ' Reinitialize array
  @(x) = x + 1
Next

Proc _MapArray (_Cosine, S)            ' Call mapping procedure

Print : For x = 0 To S - 1             ' Print results
  Print "COS(";x+1;") = ";Using "#.####";@(x)
Next

End


_MapArray Param(2)                     ' Param(1) = function
  Local (1)                            ' Param(2) = array size

  For c@ = 0 To b@ - 1
    @(c@) = FUNC(a@(@(c@)))
  Next
Return


_SquareRoot Param (1)                  ' This is an integer SQR subroutine
  Local (2)

  b@ = (10^(4*2)) * a@                 ' Output is scaled by 10^4
  a@ = b@

  Do
    c@ = (a@ + (b@ / a@))/2
  Until (Abs(a@ - c@) < 2)
    a@ = c@
  Loop

Return (c@)


_Cosine Param(1)                       ' This is an integer COS subroutine
  Push Abs((a@*10000)%62832)           ' Output is scaled by 10^4
  If Tos()>31416 Then Push 62832-Pop()
  Let a@=Tos()>15708
  If a@ Then Push 31416-Pop()
  Push Tos()
  Push (Pop()*Pop())/10000
  Push 10000+((10000*-(Tos()/56))/10000)
  Push 10000+((Pop()*-(Tos()/30))/10000)
  Push 10000+((Pop()*-(Tos()/12))/10000)
  Push 10000+((Pop()*-(Pop()/2))/10000)
  If a@ Then Push -Pop()               ' Result is directly transferred
Return                                 ' through the stack

Output:

SQRT(1) = 1.0000
SQRT(2) = 1.4142
SQRT(3) = 1.7320
SQRT(4) = 2.0000
SQRT(5) = 2.2360

COS(1) = 0.5403
COS(2) = -0.4162
COS(3) = -0.9901
COS(4) = -0.6537
COS(5) = 0.2837

0 OK, 0:514

UNIX Shell

Works with: Bourne Shell

map() {
	map_command=$1
	shift
	for i do "$map_command" "$i"; done
}
list=1:2:3
(IFS=:; map echo $list)

Works with: ksh93

Works with: pdksh

Works with: zsh

map() {
	typeset command=$1
	shift
	for i do "$command" "$i"; done
}
set -A ary 1 2 3
map print "${ary[@]}"

Works with: zsh

map(){for i ($*[2,-1]) $1 $i}
a=(1 2 3)
map print $a

Ursala

The * is a built-in map operator. This example shows a map of the successor function over a list of natural numbers.

#import nat

#cast %nL

demo = successor* <325,32,67,1,3,7,315>

Output:

<326,33,68,2,4,8,316>

V

apply squaring (dup *) to each member of collection

[1 2 3 4] [dup *] map

VBA

Option Explicit

Sub Main()
Dim arr, i
    'init
    arr = Array(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10)

    'Loop and apply a function (Fibonacci) to each element
    For i = LBound(arr) To UBound(arr): arr(i) = Fibonacci(arr(i)): Next
    
    'return
    Debug.Print Join(arr, ", ")
End Sub

Private Function Fibonacci(N) As Variant
    If N <= 1 Then
        Fibonacci = N
    Else
        Fibonacci = Fibonacci(N - 1) + Fibonacci(N - 2)
    End If
End Function

Output:

0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55

VBScript

I really have my doubts as to whether this really counts as a callback. I used the same thing in the solution to Amb.

Implementation

class callback
	dim sRule

	public property let rule( x )
		sRule = x
	end property
	
	public default function applyTo(a)
		dim p1
		for i = lbound( a ) to ubound( a )
			p1 = a( i )
			a( i ) = eval( sRule )
		next
		applyTo = a
	end function
end class

Invocation

dim a1
dim cb
set cb = new callback

cb.rule = "ucase(p1)"
a1 = split("my dog has fleas", " " )
cb.applyTo a1
wscript.echo join( a1, " " )

cb.rule = "p1 ^ p1"
a1 = array(1,2,3,4,5,6,7,8,9,10)
cb.applyto a1
wscript.echo join( a1, ", " )

Output:

MY DOG HAS FLEAS
1, 4, 27, 256, 3125, 46656, 823543, 16777216, 387420489, 10000000000

Vim Script

map() works with lists and dictionaries. The second argument is an expression string where v:val is replaced by the current value and v:key by the current key (for lists the key is the index). The result of evaluating the string will be the new value. The list/dictionary is modified in place.

echo map([10, 20, 30], 'v:val * v:val')
echo map([10, 20, 30], '"Element " . v:key . " = " . v:val')
echo map({"a": "foo", "b": "Bar", "c": "BaZ"}, 'toupper(v:val)')
echo map({"a": "foo", "b": "Bar", "c": "BaZ"}, 'toupper(v:key)')

Output:

[100, 400, 900]                                                                 
['Element 0 = 10', 'Element 1 = 20', 'Element 2 = 30']                          
{'a': 'FOO', 'b': 'BAR', 'c': 'BAZ'}                                            
{'a': 'A', 'b': 'B', 'c': 'C'}

Visual Basic .NET

Compiler: >= Visual Studio 2008

The .NET framework has got us covered.

System.Array.ForEach(T(), Action(Of T)) maps a non-value-returning callback,

System.Linq.Enumerable.Select(Of TSource,TResult)(IEnumerable(Of TSource), Func(Of TSource, TResult)) provides a way to lazily map a function, resulting in an IEnumerable(Of T),

and System.Linq.Enumerable.ToArray(Of TSource)(IEnumerable(Of TSource)) eagerly converts the enumerable to an array.

Module Program
    Function OneMoreThan(i As Integer) As Integer
        Return i + 1
    End Function

    Sub Main()
        Dim source As Integer() = {1, 2, 3}

        ' Create a delegate from an existing method.
        Dim resultEnumerable1 = source.Select(AddressOf OneMoreThan)

        ' The above is just syntax sugar for this; extension methods can be called as if they were instance methods of the first parameter.
        resultEnumerable1 = Enumerable.Select(source, AddressOf OneMoreThan)

        ' Or use an anonymous delegate.
        Dim resultEnumerable2 = source.Select(Function(i) i + 1)

        ' The sequences are the same. 
        Console.WriteLine(Enumerable.SequenceEqual(resultEnumerable1, resultEnumerable2))

        Dim resultArr As Integer() = resultEnumerable1.ToArray()

        Array.ForEach(resultArr, AddressOf Console.WriteLine)
    End Sub
End Module

Output:

True
2
3
4

Vorpal

Given and array, A, and a function, F, mapping F over the elements of A is simple:

A.map(F)

If F takes 2 arguments, x and , then simply pass them to map. They will be passed to F when as it is applied to each element of A.

A.map(F, x, y)

Wart

map prn '(1 2 3 4 5)

Output:

WDTE

let a => import 'arrays';
let s => import 'stream';

let example => [3; 5; 2];

let double => a.stream example
-> s.map (* 2)
-> s.collect
;

In WDTE, mapping can be accomplished using the stream module. Streams are essentially lazy iterators. The arrays module provides a function for creating a stream from an array, and then the stream module's functions can be used to perform a map operation. collect runs the iteration, collecting the elements yielded in a new array.

Wren

var arr = [1, 2, 3, 4, 5]
arr = arr.map { |x| x * 2 }.toList
arr = arr.map(Fn.new { |x| x / 2 }).toList
arr.each { |x| System.print(x) }

Output:

XBS

func map(arr:array,callback:function){
	set newArr:array = [];
	foreach(k,v as arr){
		newArr[k]=callback(v,k,arr);
	}
	send newArr;
}
 
set arr:array = [1,2,3,4,5];
set result:array = map(arr,func(v){
	send v*2;
});
 
log(arr.join(", "));
log(result.join(", "));

Output:

1, 2, 3, 4, 5
2, 4, 6, 8, 10

Yabasic

sub map(f$, t())
    local i

    for i = 1 to arraysize(t(), 1)
        t(i) = execute(f$, t(i))
    next i
end sub

sub add1(x)
    return x + 1
end sub

sub square(x)
    return x * x
end sub

dim t(10)

for i = 1 to 10
    t(i) = i
    print t(i), "\t";
next i
print

//map("add1", t())
map("square", t())

for i = 1 to 10
    print t(i), "\t";
next i
print

Yacas

Sin /@ {1, 2, 3, 4}

MapSingle(Sin, {1,2,3,4})

MapSingle({{x}, x^2}, {1,2,3,4})

Z80 Assembly

Array:
byte &01,&02,&03,&04,&05
Array_End:

foo:
ld hl,Array
ld b,Array_End-Array ;ld b,5

bar:
inc (hl)
inc (hl)
inc (hl)
inc hl     ;next entry in array
djnz bar

Output:

The program above doesn't show the new values but here they are:

&04,&05,&06,&07,&08

Zig

pub fn main() !void {
    var array = [_]i32{1, 2, 3}; 
    apply(@TypeOf(array[0]), array[0..], func);
}

fn apply(comptime T: type, a: []T, f: fn(T) void) void {
    for (a) |item| {
        f(item);
    }
}

fn func(a: i32) void {
    const std = @import("std");
    std.debug.print("{d}\n", .{a-1});
}

zkl

L(1,2,3,4,5).apply('+(5))

Output:

L(6,7,8,9,10)

zonnon

module Main;
type
	Callback = procedure (integer): integer;
	Vector = array {math} * of integer;

procedure Power(i:integer):integer;
begin
	return i*i;
end Power;

procedure Map(x: Vector;p: Callback): Vector;
var
	i: integer;
	r: Vector;
begin
	r := new Vector(len(x));
	for i := 0 to len(x) - 1 do	
		r[i] := p(i);
	end;
	return r
end Map;

procedure Write(x: Vector);
var
	i: integer;
begin
	for i := 0 to len(x) - 1 do
		write(x[i]:4)
	end;
	writeln
end Write;

var
	x,y: Vector;

begin
	x := [1,2,3,4,5];
	Write(Map(x,Power))
end Main.

Output:

   0   1   4   9  16

ZX Spectrum Basic

10 LET a$="x+x"
20 LET b$="x*x"
30 LET c$="x+x^2"
40 LET f$=c$: REM Assign a$, b$ or c$
150 FOR i=1 TO 5
160 READ x
170 PRINT x;" = ";VAL f$
180 NEXT i
190 STOP 
200 DATA 2,5,6,10,100