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# Apply a callback to an array

Apply a callback to an array
You are encouraged to solve this task according to the task description, using any language you may know.

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]

## 8th

The builtin word "a:map" does this:

[ 1 , 2, 3 ]
' n:sqr
a:map

That results in the array [1,4,9]

## 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);
}
}
}

Works with: GNAT version GPL 2005

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.Integer_Text_Io.Put(Item => Location, Width => 1);
Ada.Integer_Text_Io.Put(Item => Value * Value, Width => 1);
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), ¬

--> {{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
a + b

-- 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)
}

$awk 'func psqr(x){print x,x*x}BEGIN{split("1 2 3 4 5",a);for(i in a)psqr(a[i])}' 4 16 5 25 1 1 2 4 3 9 ## Babel Let us define a squaring operator: sq { dup * } < Now, we apply the sq operator over a list and display the result using the lsnum utility: ( 0 1 1 2 3 5 8 13 21 34 ) { sq ! } over ! lsnum ! Output: ( 0 1 1 4 9 25 64 169 441 1156 ) ## BBC BASIC DIM a(4) a() = 1, 2, 3, 4, 5 PROCmap(a(), FNsqrt()) FOR i = 0 TO 4 PRINT a(i) NEXT END DEF FNsqrt(n) = SQR(n) DEF PROCmap(array(), RETURN func%) LOCAL I% FOR I% = 0 TO DIM(array(),1) array(I%) = FN(^func%)(array(I%)) NEXT ENDPROC Output: 1 1.41421356 1.73205081 2 2.23606798 ## Bracmat ( ( callbackFunction1 = location value . !arg:(?location,?value) & out$(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]) ## COBOL Basic implementation of a map function: IDENTIFICATION DIVISION. PROGRAM-ID. Map. DATA DIVISION. WORKING-STORAGE SECTION. 01 Table-Size CONSTANT 30. LOCAL-STORAGE SECTION. 01 I USAGE UNSIGNED-INT. LINKAGE SECTION. 01 Table-Param. 03 Table-Values USAGE COMP-2 OCCURS Table-Size TIMES. 01 Func-Id PIC X(30). PROCEDURE DIVISION USING Table-Param Func-Id. PERFORM VARYING I FROM 1 BY 1 UNTIL Table-Size < I CALL Func-Id USING BY REFERENCE Table-Values (I) END-PERFORM GOBACK . ## 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: 0 1 4 9 16 25 36 49 64 81 0 1 16 81 256 625 1296 2401 4096 6561 ## 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) { for x in this when pred(x) { yield x } } 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 5.0 : 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... ## 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: 1 2 3 2 4 6 ## 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] ## Fōrmulæ In this page you can see the solution of this task. Fōrmulæ programs are not textual, visualization/edition of programs is done showing/manipulating structures but not text (more info). 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 transportation effects more than visualization and edition. The option to show Fōrmulæ programs and their results is showing images. Unfortunately images cannot be uploaded in Rosetta Code. ## 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)] ## 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 ## 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. ## 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]

## Lang5

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

## langur

writeln map f{^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([email protected])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);

## 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

var arr = @[1,2,3,4]
arr.apply proc(some: var int) = echo(some, " squared = ", some*some)
Output:
1 squared = 1
2 squared = 4
3 squared = 9
4 squared = 16

## 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)))

## 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
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)].

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")

return x + 1
end function

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

def map
var op
len
for
var i
i get op exec i set
endfor
enddef

1 +
enddef

def square
dup *
enddef

0 tolist
10 for
dup print 9 tochar print
0 put
endfor
nl

getid square map

10 for
get print 9 tochar print
endfor
nl

## PHP

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

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

## 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

## 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] );
}

## 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 [email protected]
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

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:

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

## 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 = "@%[email protected]"["@%[email protected]"];");
eval(""@%[email protected]"("@%[email protected]");");
}
}

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 [email protected] = 0 To [email protected] - 1 @([email protected]) = FUNC([email protected](@([email protected]))) Next Return _SquareRoot Param (1) ' This is an integer SQR subroutine Local (2) [email protected] = (10^(4*2)) * [email protected] ' Output is scaled by 10^4 [email protected] = [email protected] Do [email protected] = ([email protected] + ([email protected] / [email protected]))/2 Until (Abs([email protected] - [email protected]) < 2) [email protected] = [email protected] Loop Return ([email protected]) _Cosine Param(1) ' This is an integer COS subroutine Push Abs(([email protected]*10000)%62832) ' Output is scaled by 10^4 If Tos()>31416 Then Push 62832-Pop() Let [email protected]=Tos()>15708 If [email protected] 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 [email protected] 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: 1 2 3 4 5 ## 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: 1 2 3 4 5 ## Yabasic sub map(f$, t())
local i

for i = 1 to arraysize(t(), 1)
t(i) = execute(f$, t(i)) next i end sub sub add1(x) return x + 1 end sub sub square(x) return x * x end sub dim t(10) for i = 1 to 10 t(i) = i print t(i), "\t"; next i print //map("add1", t()) map("square", t()) for i = 1 to 10 print t(i), "\t"; next i print ## Yacas Sin /@ {1, 2, 3, 4} MapSingle(Sin, {1,2,3,4}) MapSingle({{x}, x^2}, {1,2,3,4}) ## zkl L(1,2,3,4,5).apply('+(5)) Output: L(6,7,8,9,10) ## zonnon module Main; type Callback = procedure (integer): integer; Vector = array {math} * of integer; procedure Power(i:integer):integer; begin return i*i; end Power; procedure Map(x: Vector;p: Callback): Vector; var i: integer; r: Vector; begin r := new Vector(len(x)); for i := 0 to len(x) - 1 do r[i] := p(i); end; return r end Map; procedure Write(x: Vector); var i: integer; begin for i := 0 to len(x) - 1 do write(x[i]:4) end; writeln end Write; var x,y: Vector; begin x := [1,2,3,4,5]; Write(Map(x,Power)) end Main. Output: 0 1 4 9 16 ## ZX Spectrum Basic 10 LET a$="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