Apply a callback to an array
In this task, the goal is to take a combined set of elements and apply a function to each element.
You are encouraged to solve this task according to the task description, using any language you may know.
ActionScript
<lang 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);
}
}
}</lang>
Ada
<lang ada>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;</lang>
ALGOL 68
<lang algol68> 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)
)</lang>
Output: <lang algol68>array[ +1] = +1 array[ +2] = +4 array[ +3] = +9 array[ +4] = +16</lang>
AutoHotkey
<lang AutoHotkey>map("callback", "3,4,5") callback(array) { loop, parse, array, `, msgbox % (2 * A_LoopField) }
map(callback, array) { %callback%(array) }</lang>
AWK
<lang 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</lang>
C
callback.h <lang c>#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</lang>
callback.c <lang 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;
}</lang>
Output
array[0] = 1 array[1] = 2 array[2] = 3 array[3] = 4
C#
<lang csharp>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);
}
}</lang>
This version uses the C# 3 lambda notation.
<lang csharp>int[] intArray = { 1, 2, 3, 4, 5 }; Array.ForEach(intArray, i => Console.WriteLine(i * i));</lang>
C++
C-Style Array
<lang cpp>#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</lang>
std::vector
<lang cpp>#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</lang>
More tricky with binary function <lang cpp>#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</lang>
Boost.Lambda
<lang cpp>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</lang>
Clean
Define a function and an initial (unboxed) array.
<lang clean>square x = x * x
values :: {#Int} values = {x \\ x <- [1 .. 10]}</lang>
One can easily define a map for arrays, which is overloaded and works for all kinds of arrays (lazy, strict, unboxed).
<lang clean>mapArray f array = {f x \\ x <-: array}</lang>
Apply the function to the initial array (using a comprehension) and print result.
<lang clean>Start :: {#Int} Start = mapArray square values</lang>
Common Lisp
Imperative: print 1, 2, 3, 4 and 5:
<lang lisp>(map nil #'print #(1 2 3 4 5))</lang>
Functional: collect squares into new vector that is returned:
<lang lisp>(defun square (x) (* x x)) (map 'vector #'square #(1 2 3 4 5))</lang>
Destructive, like the Javascript example; add 1 to every slot of vector *a*:
<lang lisp>(defvar *a* (vector 1 2 3)) (map-into *a* #'1+ *a*)</lang>
Clojure
<lang lisp>;; apply a named function, inc (map inc [1 2 3 4])</lang>
<lang lisp>;; apply a function (map (fn [x] (* x x)) [1 2 3 4])</lang>
<lang lisp>;; shortcut syntax for a function (map #(* % %) [1 2 3 4])</lang>
D
<lang d>U[] map(T, U)(T[] array, U delegate(T) dg) {
auto result = new U[array.length];
foreach (index, element; array)
result[index] = dg(element);
return result;
}
void main() {
writefln(
[1, 2, 3, 4, 5].map( (int i) { return i+5; } )
);
}</lang> Using std.algorithm: <lang d>writefln(map!("a + 5")([1, 2, 3, 4, 5]));</lang>
E
<lang e>def array := [1,2,3,4,5] def square(value) {
return value * value
}</lang>
Example of builtin iteration:
<lang e>def callback(index, value) {
println(`Item $index is $value.`)
} array.iterate(callback)</lang>
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).
<lang e>def map(func, collection) {
def output := [].diverge()
for item in collection {
output.push(func(item))
}
return output.snapshot()
} println(map(square, array))</lang>
Factor
Print each element squared: <lang factor>{ 1 2 3 4 } [ sq . ] each</lang>
Collect return values: <lang factor>{ 1 2 3 4 } [ sq ] map</lang>
Forth
This is a word that will call a given function on each cell in an array.
<lang forth>: map ( addr n fn -- )
-rot cells bounds do i @ over execute i ! cell +loop ;</lang>
Example usage:
<lang forth>create data 1 , 2 , 3 , 4 , 5 , data 5 ' 1+ map \ adds one to each element of data</lang>
Fortran
Elemental functions.
<lang fortran>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</lang>
<lang fortran>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</lang>
<lang fortran> 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</lang>
FP
<lang fp>{square * . [id, id]} & square: <1,2,3,4,5></lang>
F#
Apply a named function to each member of the array. The result is a new array of the same size as the input. <lang fsharp>let evenp x = x % 2 = 0 let result = Array.map evenp [| 1; 2; 3; 4; 5; 6 |]</lang> The same can be done using anonymous functions, this time squaring the members of the input array. <lang fsharp>let result = Array.map (fun x -> x * x) [|1; 2; 3; 4; 5|]</lang> Use iter if the applied function does not return a value. <lang fsharp>Array.iter (fun x -> printfn "%d" x) [|1; 2; 3; 4; 5|]</lang>
Groovy
Print each value in a list <lang groovy>[1,2,3,4].each { println it }</lang>
Create a new list containing the squares of another list <lang groovy>[1,2,3,4].collect { it * it }</lang>
Haskell
List
<lang haskell>let square x = x*x let values = [1..10] map square values</lang>
Using list comprehension to generate a list of the squared values <lang haskell>[square x | x <- values]</lang>
Using function composition to create a function that will print the squares of a list <lang haskell>let printSquares = mapM_ (print.square) printSquares values</lang>
Array
<lang haskell>import Data.Array.IArray let square x = x*x let values = array (1,10) [(i,i)|i <- [1..10]] :: Array Int Int amap square values</lang>
Icon
<lang icon>procedure main()
local lst lst := [10, 20, 30, 40] every callback(!lst)
end
procedure callback(arg)
write("->", arg)
end</lang>
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
<lang idl>b = a^3</lang>
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
<lang io>list(1,2,3,4,5) map(squared)</lang>
J
Solution: <lang j> "_1</lang>
Example: <lang j> callback =: *:
array =: 1 2 3 4 5 callback"_1 array
1 4 9 16 25</lang>
Java
As of the current version of Java, you have to define an interface for each type of function you want to use. The next version of Java will introduce function types.
So if you want to perform an action (which doesn't return anything) on an array of int's:
<lang java>interface IntToVoid {
void run(int x);
}
for (int z : myIntArray) {
new IntToVoid() {
public void run(int x) {
System.out.println(x);
}
}.run(z);
}</lang>
Or if you want to perform "map" - return an array of the results of function applications:
<lang java>interface IntToInt {
int run(int x);
}
int[] result = new int[myIntArray.length]; for (int i = 0; i < myIntArray.length; i++) {
result[i] =
new IntToInt() {
public int run(int x) {
return x * x;
}
}.run(myIntArray[i]);
}</lang>
JavaScript
Portable technique:
<lang javascript>function map(a, func) {
for (var i in a) a[i] = func(a[i]);
}
var a = [1, 2, 3, 4, 5]; map(a, function(v) { return v * v; });</lang>
With the BeyondJS library:
<lang javascript>var a = (1).to(10).collect(Math.pow.curry(undefined,2));</lang>
With Firefox 2.0:
<lang javascript>function cube(num) {
return Math.pow(num, 3);
}
var numbers = [1, 2, 3, 4, 5];
// get results of calling cube on every element var cubes1 = numbers.map(cube);
// display each result in a separate dialog cubes1.forEach(alert);
// array comprehension var cubes2 = [cube(n) for each (n in numbers)]; var cubes3 = [n * n * n for each (n in numbers)];</lang>
<lang javascript>Functional.map('x*x*x', [1,2,3,4,5])</lang>
Joy
<lang joy>[1 2 3 4 5] [dup *] map.</lang>
Lisaac
<lang Lisaac>+ a : ARRAY[INTEGER]; + b : BLOCK;
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;</lang>
Logo
<lang 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</lang>
Lua
Say we have an array: <lang lua>myArray = {1, 2, 3, 4, 5}</lang> A map function for this would be <lang lua>map = function(f, data)
local result = {}
for k,v in ipairs(data) do
result[k] = f(v)
end
return result
end</lang> Together with our array and a square function this yields: <lang lua>myFunc = function(x) return x*x end
print(unpack( map(myFunc, myArray) )) --> 1 4 9 16 25</lang> If you used pairs() instead of ipairs(), this would even work on a hash table in general.
M4
<lang 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')</lang>
Output:
2 4 6
Modula-3
<lang modula3>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.</lang>
Nial
<lang nial>each (* [first, first] ) 1 2 3 4 =1 4 9 16</lang>
OCaml
This function is part of the standard library:
<lang ocaml>Array.map</lang>
Usage example: <lang ocaml>let square x = x * x;; let values = Array.init 10 ((+) 1);; Array.map square values;;</lang>
Or with lists (which are more typical in OCaml): <lang ocaml>let values = [1;2;3;4;5;6;7;8;9;10];; List.map square values;;</lang>
Use iter if the applied function does not return a value.
<lang ocaml>Array.iter (fun x -> Printf.printf "%d" x) [|1; 2; 3; 4; 5|];;</lang> <lang ocaml>List.iter (fun x -> Printf.printf "%d" x) [1; 2; 3; 4; 5];;</lang>
with partial application we can also write:
<lang ocaml>Array.iter (Printf.printf "%d") [|1; 2; 3; 4; 5|];;</lang> <lang ocaml>List.iter (Printf.printf "%d") [1; 2; 3; 4; 5];;</lang>
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.
<lang octave>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</lang>
(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)))
Oz
<lang oz>functor import
Application System
define
Print = System.showInfo
fun{Square A}
A*A
end
fun{FuncEach Func A}
{Map A Func}
end
proc{ProcEach Proc A}
{ForAll A Proc}
end
Arr = [1 2 3 4 5]
{ProcEach Print {FuncEach Square Arr}}
{ForAll {Map Arr Square} Print} %% same
{Application.exit 0}
end</lang>
Perl
<lang perl># create array my @a = (1, 2, 3, 4, 5);
- create callback function
sub mycallback {
return 2 * shift;
}
- use array indexing
my $i; for ($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)</lang>
Perl 6
<lang perl6>my $function = { 2*$^x + 3 }; my @array = 1 .. 5;
.say for map $function, @array;
.say for @array.map($function);
for @array {
say $function($_);
}</lang>
PHP
<lang php>function cube($n) {
return($n * $n * $n);
}
$a = array(1, 2, 3, 4, 5); $b = array_map("cube", $a); print_r($b);</lang>
PL/SQL
<lang plsql>set serveroutput on declare
type myarray is table of number index by binary_integer;
x myarray;
i pls_integer;
begin
-- populate array
for i in 1..5 loop
x(i) := i;
end loop;
i :=0;
-- square array
loop
i := i + 1;
begin
x(i) := x(i)*x(i);
dbms_output.put_line(x(i));
exception
when no_data_found then exit;
end;
end loop;
end; /</lang>
Pop11
<lang 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);</lang>
If one wants to create a new array consisting of transformed values then procedure mapdata may be more convenient.
PowerShell
This can be done in PowerShell with the ForEach-Object cmdlet which applies a scriptblock to each element of an array:
<lang powershell>1..5 | ForEach-Object { $_ * $_ }</lang>
To recreate a map function, found in other languages the same method applies:
<lang powershell>function map ([array] $a, [scriptblock] $s) {
$a | ForEach-Object $s
}</lang>
Python
<lang 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</lang> To print squares of integers in the range from 0 to 9, type: <lang python>print " ".join(str(n * n) for n in range(10))</lang> Or: <lang python>print " ".join(map(str, map(square, range(10))))</lang> Result: <lang python>0 1 4 9 16 25 36 49 64 81</lang>
R
Many functions can take advantage of implicit vectorisation, e.g. <lang R>cube <- function(x) x*x*x elements <- 1:5 cubes <- cube(elements)</lang> Explicit looping over array elements is also possible. <lang R>cubes <- numeric(5) for(i in seq_along(cubes)) {
cubes[i] <- cube(elements[i])
}</lang> Loop syntax can often simplified using the *array family of functions. <lang R>elements2 <- list(1,2,3,4,5) cubes <- sapply(elements2, cube)</lang> In each case above, the value of 'cubes' is
1 8 27 64 125
Raven
<lang raven># To print the squared elements [1 2 3 4 5] each dup * print</lang>
<lang raven># To obtain a new array group [1 2 3 4 5] each
dup *
list</lang>
Ruby
You could use a traditional "for i in arr" approach like below: <lang ruby>for i in [1,2,3,4,5] do
puts i**2
end</lang>
Or you could the more preferred ruby way of an iterator (which is borrowed from SmallTalk) <lang ruby>[1,2,3,4,5].each{ |i| puts i**2 }</lang>
To create a new array of each value squared <lang ruby>[1,2,3,4,5].map{ |i| i**2 }</lang>
Scala
<lang scala>val l = List(1,2,3,4) l.foreach {i => println(i)}</lang>
When the argument appears only once -as here, i appears only one in println(i) - it may be shortened to <lang scala>l.foreach(println(_))</lang> Same for an array <lang scala>val a = Array(1,2,3,4) a.foreach {i => println(i)} a.foreach(println(_)) // same as previous line</lang>
Or for an externally defined function: <lang scala>def doSomething(in: int) = {println("Doing something with "+in)} l.foreach(doSomething)</lang>
There is also a for syntax, which is internally rewritten to call foreach. A foreach method must be defined on a <lang scala>for(val i <- a) println(i)</lang>
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) <lang scala>val squares = l.map{i => i * i} //squares is List(1,4,9,16)</lang>
Or the equivalent for syntax, with the additional keyword yield, map is called instead of foreach <lang scala>val squares = for (val i <- l) yield i * i</lang>
Scheme
<lang scheme>(define (square n) (* n n)) (define x #(1 2 3 4 5)) (map square (vector->list x))</lang>
A single-line variation <lang scheme>(map (lambda (n) (* n n)) '(1 2 3 4 5))</lang>
For completeness, the map function (which is R5RS standard) can be coded as follows: <lang scheme>(define (map f L)
(if (null? L)
L
(cons (f (car L)) (map f (cdr L)))))</lang>
Slate
<lang slate>#( 1 2 3 4 5 ) collect: [| :n | n * n].</lang>
Smalltalk
<lang smalltalk>#( 1 2 3 4 5 ) collect: [:n | n * n].</lang>
Tcl
If I wanted to call "myfunc" on each element of dat and dat were a list:
<lang tcl>foreach var $dat { myfunc $var }</lang>
if dat were an array, however:
<lang tcl>foreach name [array names dat] { myfunc $dat($name) }</lang>
More functional, with a simple map function: <lang Tcl>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</lang>
TI-89 BASIC
<lang ti89b>© 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})</lang>
Output:
Toka
<lang 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</lang>
Ursala
The * is a built-in map operator. This example shows a map of the successor function over a list of natural numbers. <lang Ursala>#import nat
- cast %nL
demo = successor* <325,32,67,1,3,7,315></lang> output:
<326,33,68,2,4,8,316>
V
apply squaring (dup *) to each member of collection <lang v>[1 2 3 4] [dup *] map</lang>
Vorpal
Given and array, A, and a function, F, mapping F over the elements of A is simple: <lang vorpal>A.map(F)</lang> 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. <lang vorpal>A.map(F, x, y)</lang>