Loops/Foreach: Difference between revisions

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Loop through and print each element in a collection in order.

Use your language's "for each" loop if it has one, otherwise iterate through the collection in order with some other loop.

Related tasks

ACL2

<lang Lisp>(defun print-list (xs)

  (if (endp xs)
      nil
      (prog2$ (cw "~x0~%" (first xs))
              (print-list (rest xs)))))</lang>

> (print-list (list 1 "a" 1/2 (list 1 2) 'sym))
1
"a"
1/2
(1 2)
SYM
NIL

Aikido supports coroutines. The foreach operator may be used to iterate thorough the generated values. <lang aikido>// coroutine to generate the squares of a sequence of numbers function squares (start, end) {

   for (var i = start ; i < end ; i++) {
       yield i*i
   }

}

var start = 10 var end = 20

foreach s squares (start, end) {

   println (s)

}</lang>

Files

If you open a file you can iterate through all the lines <lang aikido>var s = openin ("input.txt") foreach line s {

   print (line)

}</lang>

Enumerations

<lang aikido>enum Color {

  RED, GREEN, BLUE

}

foreach color Color {

   println (color)

}</lang>

Aime

<lang aime># iterate over a list of integers integer i, v;

for (i, v in list(2, 3, 5, 7, 11, 13, 17, 18)) { }</lang>

ALGOL 68

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

Works with: ALGOL 68G version Any - tested with release mk15-0.8b.fc9.i386

Works with: ELLA ALGOL 68 version Any (with appropriate job cards) - tested with release 1.8.8d.fc9.i386

<lang algol68>[]UNION(STRING, INT, PROC(REF FILE)VOID) collection = ("Mary","Had",1,"little","lamb.",new line);

FOR index FROM LWB collection TO UPB collection DO

 print((collection[index]," "))

OD</lang> Output:

Mary Had          +1 little lamb.

Note: ALGOL 68S actually has a reserved word FOREACH that is used to break arrays in to portions, and process in parallel.

AmigaE

<lang amigae>PROC main()

 DEF a_list : PTR TO LONG, a
 a_list := [10, 12, 14]
 FOR a := 0 TO ListLen(a_list)-1
   WriteF('\d\n', a_list[a])
 ENDFOR
 -> if the "action" fits a single statement, we can do instead
 ForAll({a}, a_list, `WriteF('\d\n', a))

ENDPROC</lang>

Apex

<lang Apex> Integer[] myInts = new Integer[]{1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

for (Integer i : myInts) {

   System.debug(i);

} </lang>

AppleScript

<lang AppleScript>repeat with fruit in {"Apple", "Orange", "Banana"}

 log contents of fruit

end repeat</lang>

Arturo

<lang arturo>array #("one" "two" "three")

dict #{ name "john" surname "doe" age 33 }

loop array { print & }

loop dict [key,val]{ print key + " => " + val }</lang>

Output:

one
two
three
surname => doe
age => 33
name => john

AutoHotkey

<lang AutoHotkey>string = mary,had,a,little,lamb Loop, Parse, string, `,

 MsgBox %A_LoopField%</lang>

AWK

The for (element_index in array) can be used, but it does not give elements' indexes in the order inside the array (AWK indexes in array are indeed more like hashes). <lang awk> BEGIN {

 split("Mary had a little lamb", strs, " ")
 for(el in strs) {
   print strs[el]
 }

}</lang> If elements must be returned in some order, keys must be generated in that order. In the example above the array is filled through the split function, which uses indexes from 1. So to iterate over the array's elements in the right order, a normal loop can be used: <lang awk>BEGIN {

 n = split("Mary had a little lamb", strs, " ")
 for(i=1; i <= n; i++) {
   print strs[i]
 }

}</lang>

Note that in awk, foreach loops can only be performed against an associative container. It is not possible to loop against an explicit list, so the following will not work:

<lang awk># This will not work BEGIN {

 for (l in "apples","bananas","cherries") {
 print "I like " l

}</lang>

BASIC

BASIC256

BASIC-256 does not have a FOR EACH type statement. Use a FOR loop to iterate through an array by index. <lang BASIC256>DIM collection$(1) collection$ = { "The", "quick", "brown", "fox", "jumps", "over", "the", "lazy", "dog." }

FOR i = 0 TO collection$[?]-1

  PRINT collection$[i]+ " ";

NEXT i PRINT</lang> Output:

The quick brown fox jumps over the lazy dog.

BBC BASIC

Works with: BBC BASIC for Windows

<lang bbcbasic> DIM collection$(8)

     collection$() = "The", "quick", "brown", "fox", "jumps", \
     \               "over", "the", "lazy", "dog."
     
     FOR index% = 0 TO DIM(collection$(), 1)
       PRINT collection$(index%) " ";
     NEXT
     PRINT</lang>

Commodore BASIC

Commodore BASIC too does not have a FOR-EACH construct. FOR loop is used to iterate through a string array by index. READ-DATA is used to fill up the string array <lang qbasic>10 DIM A$(9) :REM DECLARE STRING ARRAY 20 REM *** FILL ARRAY WITH WORDS *** 30 FOR I = 0 TO 8 40 READ A$(I) 50 NEXT 60 REM *** PRINT ARRAY CONTENTS *** 70 FOR I = 0 TO 8 80 PRINT A$(I)" "; 90 NEXT 100 END 1000 DATA THE, QUICK, BROWN, FOX, JUMPS, OVER, THE, LAZY, DOG.</lang>

Creative Basic

<lang Creative Basic>DEF AnArray[11]:INT

AnArray=0,1,2,3,4,5,6,7,8,9,10

'A console only program will work without OPENCONSOLE and 'CLOSECONSOLE; however, it does not hurt to use them. OPENCONSOLE

FOR X=0 TO 10

   PRINT AnArray[X]

NEXT X

'keep the console from closing right away. DO:UNTIL INKEY$<>""

CLOSECONSOLE

'because this is a console only program. END </lang>

FreeBASIC

<lang freebasic>' FB 1.05.0

' FreeBASIC doesn't have a foreach loop but it's easy to manufacture one using macros

Macro ForEach(I, A)

For _i as integer = LBound(A) To UBound(A)

Define I (A(_i))
EndMacro

Define In ,

Dim a(-5 To 5) As Integer = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11} ForEach(i in a)

 Print i; " ";

Output:

 1  2  3  4  5  6  7  8  9  10  11

Gambas

Click this link to run this code <lang gambas>Public Sub Main() Dim siInput As Short[] = [1, 8, 0, 6, 4, 7, 3, 2, 5, 9] Dim siTemp As Short

For Each siTemp In siInput.Sort()

 Print siTemp;;

Output:

0 1 2 3 4 5 6 7 8 9

IS-BASIC

<lang IS-BASIC>100 STRING COLLECTION$(1 TO 9)*8 110 LET I=1 120 DO 130 READ IF MISSING EXIT DO:COLLECTION$(I) 140 LET I=I+1 150 LOOP 160 FOR J=1 TO I-1 170 PRINT COLLECTION$(J);" "; 180 NEXT 190 DATA The,quick,brown,fox,jumps,over,the,lazy,dog.</lang>

IWBASIC

Linked List <lang IWBASIC>DEF AList:POINTER

AList=ListCreate()

'Add items to the list. DEF X:INT

FOR X=0 TO 10

   POINTER Temp=ListAdd(AList,NEW(INT,1))
   #<INT>temp=X

'The hash ("#") dereferencing operator is unique to IWBASIC and Creative Basic, and 'it is suitable for most basic pointer needs. IWBASIC also supports a "C style" 'dereferencing operator: "*". And that will work here too. NEXT X

'A program compiled as console only does not need the commands to open and 'close the console. However, it does not hurt to use them. OPENCONSOLE

'***Iterate the list with the "for each" loop*** FOR Temp=EACH AList AS INT

    PRINT #Temp

'A press any key to continue message is automatic in a program compiled as a console only program. I presume the compiler inserts the code. CLOSECONSOLE

'Because this is a console only program. END</lang>

An Array <lang IWBASIC>DEF AnArray[11]:INT

AnArray=0,1,2,3,4,5,6,7,8,9,10

OPENCONSOLE

FOR X=0 TO 10 PRINT AnArray[X] NEXT X

PRINT

'a press any key message is automatic when compiled as console only. CLOSECONSOLE

'Because this is a console only program. END </lang>

Liberty BASIC

The most natural way is to use a csv list with a sentinel value. <lang lb>in$ ="Not,Hardly,Just,Adequately,Quite,Really,Very,Fantastically,xyzzy" element$ ="" i =1 ' used to point to successive elements

do

   element$ =word$( in$, i, ",")
   if element$ ="xyzzy" then exit do
   print element$; " good!"
   i =i +1

loop until 1 =2

end</lang>

Not good!
Hardly good!
Just good!
Adequately good!
Quite good!
Really good!
Very good!
Fantastically good!

NS-HUBASIC

<lang NS-HUBASIC>10 DIM A$(9) : REM DECLARE STRING ARRAY 20 REM ADD DATA TO ARRAY AND PRINT ARRAY CONTENTS 30 FOR I=0 TO 8 40 READ A$(I) 50 PRINT A$(I)" "; 60 NEXT 70 DATA THE, QUICK, BROWN, FOX, JUMPS, OVER, THE, LAZY, DOG.</lang>

PureBasic

Works for LinkedLists and Maps <lang PureBasic>ForEach element()

 PrintN(element())

Next</lang>

Run BASIC

<lang runbasic>t$={Sunday,Monday,Tuesday,Wednesday,Thursday,Friday,Saturday"

while word$(t$,i+1,",") <> ""

 i = i + 1
 print word$(t$,i,",")

wend</lang>

TI-89 BASIC

<lang ti89b>Local i,strs Define strs = {"Lorem","ipsum","dolor"} For i, 1, dim(strs)

 Disp strs[i]

EndFor</lang>

VBA

<lang VB>Public Sub LoopsForeach()

   Dim FruitArray() As Variant
   Dim Fruit As Variant
   FruitArray = [{"Apple","Banana","Strawberry"}]
   Dim FruitBasket As Collection
   Set FruitBasket = New Collection
   For Each Fruit In FruitArray
       FruitBasket.Add Fruit
   Next Fruit
   For Each Fruit In FruitBasket
       Debug.Print Fruit
   Next Fruit

End Sub</lang>

VBScript

<lang vbscript>items = Array("Apple", "Orange", "Banana")

For Each x In items

   WScript.Echo x

Next</lang>

Visual Basic .NET

<lang vbnet>Dim list As New List(Of String) list.Add("Car") list.Add("Boat") list.Add("Train")

For Each item In list

   Console.WriteLine(item)

Next</lang>

Batch File

The FOR command can imitate the "Foreach Loop". The whitespace and the comma (,) are the default delimiters.

Direct usage: <lang dos>@echo off for %%A in (This is a sample collection) do (

    echo %%A

)</lang> Using a Collection Variable: <lang dos>@echo off set "collection=This is a sample collection" for %%A in (%collection%) do (

    echo %%A

)</lang>

They have the Same Output:

This
is
a
sample
collection

bc

There is no "for each"-loop in bc. For accessing each element of an array (the only collection-like type) one uses a straightforward for-loop. <lang bc>a[0] = .123 a[1] = 234 a[3] = 95.6 for (i = 0; i < 4; i++) {

   a[i]

}</lang>

Bracmat

Bracmat has a more or less traditional 'while' loop (whl'expression) which was introduced rather late in the history of Bracmat. Before that, tail recursion was a way to repeat something. But let us make a list first: <lang bracmat> ( list

 =   Afrikaans
     Ελληνικά
     עברית
     മലയാളം
     ئۇيغۇرچە
 )</lang>

The 'while' solution. Use an auxiliary variable L that gets its head chopped off until nothing is left: <lang bracmat> !list:?L & whl'(!L:%?language ?L&out$!language)</lang> The tail-recursive solution. When the auxiliary variable is reduced to nothing, the loop fails. By adding the ~ flag to the initial invocation, failure is turned into success. This solution benefits from tail recursion optimization. <lang bracmat> !list:?L & ( loop

 =   !L:%?language ?L
   & out$!language
   & !loop
 )

& ~!loop</lang> A completely different way of iteration is by using a pattern that matches an element in the list, does something useful as a side effect and then fails, forcing bracmat to backtrack and try the next element in the list. The @ flag matches at most one element. The % flag matches at least one element. Together they ensure that exactly one language name is assigned to the variable language. After all elements have been done, control is passed to the rhs of the | operator. <lang bracmat> ( !list

   : ? (%@?language&out$!language&~) ?
 | 
 )</lang>

C

C does not really have a native 'container' type, nor does it have a 'for each' type statement. The following shows how to loop through an array and print each element. <lang c>#include <stdio.h> ...

const char *list[] = {"Red","Green","Blue","Black","White"};

define LIST_SIZE (sizeof(list)/sizeof(list[0]))

int ix; for(ix=0; ix<LIST_SIZE; ix++) {

  printf("%s\n", list[ix]);

}</lang>

The C language does, however, have a number of standard data structures that can be thought of as collections, and foreach can easily be made with a macro.

C string as a collection of char <lang c>

include <stdio.h>
include <stdlib.h>

/* foreach macro for using a string as a collection of char */

define foreach( ptrvar , strvar ) char* ptrvar; for( ptrvar=strvar ; (*ptrvar) != '\0' ; *ptrvar++)

int main(int argc,char* argv[]){ char* s1="abcdefg"; char* s2="123456789"; foreach( p1 , s1 ) {

printf("loop 1 %c\n",*p1);

} foreach( p2 , s2 ){

printf("loop 2 %c\n",*p2);

} exit(0); return(0); } </lang>

C int array as a collection of int (array size known at compile-time) <lang c>

include <stdio.h>
include <stdlib.h>

int main(int argc,char* argv[]){ /* foreach macro viewing an array of int values as a collection of int values */

define foreach( intpvar , intary ) int* intpvar; for( intpvar=intary; intpvar < (intary+(sizeof(intary)/sizeof(intary[0]))) ; intpvar++)

int a1[]={ 1 , 1 , 2 , 3 , 5 , 8 }; int a2[]={ 3 , 1 , 4 , 1, 5, 9 }; foreach( p1 , a1 ) {

printf("loop 1 %d\n",*p1);

} foreach( p2 , a2 ){

printf("loop 2 %d\n",*p2);

} exit(0); return(0); } </lang>

Most general: string or array as collection (collection size known at run-time)

Note: idxtype can be removed and typeof(col[0]) can be used in it's place with GCC

include <stdio.h>
include <stdlib.h>
include <string.h>

int main(int argc,char* argv[]){

define foreach( idxtype , idxpvar , col , colsiz ) idxtype* idxpvar; for( idxpvar=col ; idxpvar < (col+(colsiz)) ; idxpvar++)
define arraylen( ary ) ( sizeof(ary)/sizeof(ary[0]) )

char* c1="collection"; int c2[]={ 3 , 1 , 4 , 1, 5, 9 }; double* c3; int c3len=4; c3=(double*)calloc(c3len,sizeof(double)); c3[0]=1.2;c3[1]=3.4;c3[2]=5.6;c3[3]=7.8; foreach( char,p1 , c1, strlen(c1) ) {

printf("loop 1 : %c\n",*p1);

} foreach( int,p2 , c2, arraylen(c2) ){

printf("loop 2 : %d\n",*p2);

} foreach( double,p3 , c3, c3len ){

printf("loop 3 : %3.1lf\n",*p3);

} exit(0); return(0); } </lang>

C++

C++03 did not have a "for each" loop. The following is a generic loop which works with any standard container except for built-in arrays. The code snippet below assumes that the container type in question is typedef'd to container_type and the actual container object is named container. <lang cpp>for (container_type::iterator i = container.begin(); i != container.end(); ++i) {

 std::cout << *i << "\n";

}</lang> However the idiomatic way to output a container would be <lang cpp>std::copy(container.begin(), container.end(),

         std::ostream_iterator<container_type::value_type>(std::cout, "\n"));</lang>

There's also an algorithm named for_each. However, you need a function or function object to use it, e.g. <lang cpp>void print_element(container_type::value_type const& v) {

 std::cout << v << "\n";

}

...

 std::for_each(container.begin(), container.end(), print_element);</lang>

Works with: C++11

<lang cpp>for (auto element: container) {

 std::cout << element << "\n";

}</lang> Here container is the container variable, element is the loop variable (initialized with each container element in turn), and auto means that the compiler should determine the correct type of that variable automatically. If the type is expensive to copy, a const reference can be used instead: <lang cpp>for (auto const& element: container) {

 std::cout << element << "\n";

}</lang> Of course the container elements can also be changed by using a non-const reference (provided the container isn't itself constant): <lang cpp>for (auto&& element: container) //use a 'universal reference' {

 element += 42;

}</lang>

C#

<lang csharp>string[] things = {"Apple", "Banana", "Coconut"};

foreach (string thing in things) {

   Console.WriteLine(thing);

}</lang>

Chapel

<lang chapel>var food = ["Milk", "Bread", "Butter"]; for f in food do writeln(f);</lang>

Clojure

<lang lisp>(doseq [item collection] (println item))</lang>

CMake

<lang cmake>set(list one.c two.c three.c)

foreach(file ${list})

 message(${file})

endforeach(file)</lang>

COBOL

The following is in the Managed COBOL dialect:

Translation of: C#

Works with: Visual COBOL

<lang cobol>01 things occurs 3. ... set content of things to ("Apple", "Banana", "Coconut") perform varying thing as string through things

   display thing

end-perform</lang>

ColdFusion

 <Cfoutput>#i#!</Cfoutput>

</Cfloop> </lang>

Common Lisp

<lang lisp>(loop for i in list do (print i))</lang> or <lang lisp>(map nil #'print list)</lang>

D

This works if collection is a string/array/associative array, or if implements an appropriate opApply function, or if it has the basic Range methods. <lang d>import std.stdio: writeln;

void main() {

   auto collection1 = "ABC";
   foreach (element; collection1) 
       writeln(element);

   auto collection2 = [1, 2, 3];
   foreach (element; collection1) 
       writeln(element);

   auto collection3 = [1:10, 2:20, 3:30];
   foreach (element; collection3) 
       writeln(element);

   foreach (key, value; collection3)
       writeln(key, " ", value);

}</lang>

Output:

Dao

<lang dao>items = { 1, 2, 3 } for( item in items ) io.writeln( item )</lang>

Delphi

for..in loops were added in Delphi 2005.

Supports arrays (single, multidimensional, and dynamic), sets, strings, collections and any class or interface that implements GetEnumerator(). <lang Delphi>program LoopForEach;

{$APPTYPE CONSOLE}

var

 s: string;

begin

 for s in 'Hello' do
   Writeln(s);

end.</lang> Output:

H
e
l
l
o

Dragon

<lang dragon> for (value : array) {

  showln array

} </lang>

Dyalect

<lang Dyalect>for i in [1,2,3] {

  print(i)

}</lang>

This code would work for any type that has a method "iter" (returning an iterator). In fact a runtime environment silently calls this method for you here and creates an iterator out of an array. The code above is absolutely identical to:

<lang Dyalect>for i in [1,2,3].iter() {

  print(i)

}</lang>

This would perfectly work with any custom iterator as well:

<lang Dyalect>func myCollection() {

   yield 1
   yield 2
   yield 3

}

for i in myCollection() {

  print(i)

}</lang>

All three code samples would output:

1
2
3

E

<lang e>for e in theCollection {

   println(e)

}</lang> In E, the for ... in ... loop is also used for iterating over numeric ranges; see Loop/For#E.

EchoLisp

<lang scheme> (define my-list '( albert simon antoinette)) (for ((h my-list)) (write h))

   albert simon antoinette

(define my-vector #(55 66 soixante-dix-sept)) (for (( u my-vector)) (write u))

   55 66 soixante-dix-sept

(define my-string "Longtemps") (for ((une-lettre my-string)) (write une-lettre))

   "L" "o" "n" "g" "t" "e" "m" "p" "s"

etc ... for other collections like Streams, Hashes, Graphs, ...

</lang>

Efene

Any data structure can be printed as a whole, preformated: <lang efene>io.format("~p~n", [Collection])</lang> However, to iterate over each element of a list, Efene uses lists.map/2, except in the case of IO where lists.foreach/2 has to be used as the evaluation order is defined to be the same as the order of the elements in the list. <lang efene>lists.foreach(fn (X) { io.format("~p~n", [X]) }, Collection)</lang>

Eiffel

Works with: EiffelStudio version 6.6 beta (with provisional loop syntax)

The iteration (foreach) form of the Eiffel loop construct is introduced by the keyword across. <lang eiffel > across my_list as ic loop print (ic.item) end</lang> The local entity ic is an instance of the library class ITERATION_CURSOR. The cursor's feature item provides access to each structure element. Descendants of class ITERATION_CURSOR can be created to handle specialized iteration algorithms. The types of objects that can be iterated across (my_list in the example) are based on classes that inherit from the library class ITERABLE

Boolean expression variant

The iteration form of the Eiffel loop can also be used as a boolean expression when the keyword loop is replaced by either all (effecting universal quantification) or some (effecting existential quantification).

This iteration is a boolean expression which is true if all items in my_list have counts greater than three: <lang eiffel> across my_list as ic all ic.item.count > 3 end</lang> Whereas, the following is true if at least one item has a count greater than three: <lang eiffel> across my_list as ic some ic.item.count > 3 end</lang>

Ela

<lang ela>open monad io

each [] = do return () each (x::xs) = do

 putStrLn $ show x
 each xs</lang>

Elena

ELENA 4.1 : <lang elena>import system'routines; import extensions;

public program() {

   var things := new string[]::("Apple", "Banana", "Coconut");

   things.forEach:(thing)
   {
       console.printLine:thing
   }

}</lang>

Elixir

<lang elixir>iex(1)> list = [1,3.14,"abc",[3],{0,5}] [1, 3.14, "abc", [3], {0, 5}] iex(2)> Enum.each(list, fn x -> IO.inspect x end) 1 3.14 "abc" [3] {0, 5}

ok</lang>

Emacs Lisp

For a list either dolist macro

<lang Lisp>(dolist (x '(1 2 3 4))

 (message "x=%d" x))</lang>

or mapc function

<lang Lisp>(mapc (lambda (x)

       (message "x=%d" x))
     '(1 2 3 4))</lang>

dolist and mapc are both builtin in current Emacs. For past Emacs both can be had from cl.el with for instance (eval-when-compile (require 'cl)).

cl.el also offers a loop macro similar in style to Common Lisp.

Erlang

Any data structure can be printed as a whole, preformated: <lang erlang>io:format("~p~n",[Collection]).</lang> However, to iterate over each element of a list, Erlang uses lists:map/2, except in the case of IO where lists:foreach/2 has to be used as the evaluation order is defined to be the same as the order of the elements in the list. <lang erlang>lists:foreach(fun(X) -> io:format("~p~n",[X]) end, Collection).</lang>

ERRE

It's an extension of 'standard' FOR loop: constant list must be explicit. <lang ERRE>

     FOR INDEX$=("The","quick","brown","fox","jumps","over","the","lazy","dog.") DO
       PRINT(INDEX$;" ";)
     END FOR
     PRINT

</lang>

Euphoria

Works with: OpenEuphoria

<lang> include std/console.e

sequence s = {-2,-1,0,1,2} --print elements of a numerical list for i = 1 to length(s) do ? s[i] end for

puts(1,'\n')

s = {"Name","Date","Field1","Field2"} -- print elements of a list of 'strings' for i = 1 to length(s) do printf(1,"%s\n",{s[i]}) end for

puts(1,'\n')

for i = 1 to length(s) do -- print subelements of elements of a list of 'strings' for j = 1 to length(s[i]) do printf(1,"%s\n",s[i][j]) end for puts(1,'\n') end for

if getc(0) then end if </lang>

Output:

-2
-1
0
1
2

Name
Date
Field1
Field2

N
a
m
e

D
a
t
e

F
i
e
l
d
1

F
i
e
l
d
2

Factor

Fantom

Use each method to iterate over a collection of items in a List. <lang fantom>class Main {

 public static Void main ()
 {
   Int[] collection := [1, 2, 3, 4, 5]
   collection.each |Int item|
   {
     echo (item)
   }
 }

}</lang>

friendly interactive shell

Unlike, bash or csh, the PATH variable is automatically converted to real array. <lang fishshell>for path in $PATH

   echo You have $path in PATH.

end</lang>

Sample output:

You have /bin in PATH.
You have /usr/bin in PATH.

Fortran

<lang fortran>program main

implicit none

integer :: i
character(len=5),dimension(5),parameter :: colors = ['Red  ','Green','Blue ','Black','White']

!using a do loop:
do i=1,size(colors)
  write(*,'(A)') colors(i) 
end do

!this will also print each element:
write(*,'(A)') colors

end program main</lang>

Forth

<lang forth>create a 3 , 2 , 1 ,

.array ( a len -- )

 cells bounds do  i @ .  cell +loop ;     \ 3 2 1</lang>

Frink

Frink's for loop is actually a "for each" loop which can iterate over built-in collection types including arrays, sets, dictionaries, enumerating expressions, and Java types such as Map, Iterator, Enumeration, etc. <lang frink> array = [1, 2, 3, 5, 7] for n = array

  println[n]

</lang>

F#

We can use for directly or list iteration. <lang fsharp>for i in [1 .. 10] do printfn "%d" i

List.iter (fun i -> printfn "%d" i) [1 .. 10]</lang>

GAP

<lang gap>for p in AlternatingGroup(4) do

   Print(p, "\n");

od;

() (1,3,2) (1,2,3) (1,4,3) (2,4,3) (1,3)(2,4) (1,2,4) (1,4)(2,3) (2,3,4) (1,3,4) (1,2)(3,4) (1,4,2)</lang>

Go

range works with all of the built-in container-types. With one variable (i), it gives you the key/index of every item. With two variables (i, x), it gives you both the key/index and value/item. For channels, only the single-variable variant is allowed. <lang go>func printAll(values []int) {

  for i, x := range values {
     fmt.Printf("Item %d = %d\n", i, x)
  }

}</lang>

Groovy

"for" loop: <lang groovy>def beatles = ["John", "Paul", "George", "Ringo"]

for(name in beatles) {

   println name

}</lang> "each()" method:
Though technically not a loop, most Groovy programmers would use the somewhat more terse "each()" method on the list itself in preference to the "for" loop construct. <lang groovy>beatles.each {

   println it

}</lang> Output (same for either):

John
Paul
George
Ringo

Halon

<lang halon>$things = ["Apple", "Banana", "Coconut"];

foreach ($things as $thing) {

   echo $thing;

}</lang>

Haskell

<lang haskell>import Control.Monad (forM_) forM_ collect print</lang> which is the same as <lang haskell>mapM_ print collect</lang>

Haxe

<lang haxe>var a = [1, 2, 3, 4];

for(i in a)

   Sys.println(i);</lang>

HicEst

<lang hicest>CHARACTER days="Monday Tuesday Wednesday Thursday Friday Saturday Sunday "

items = INDEX(days, ' ', 256) ! 256 = count option DO j = 1, items

 EDIT(Text=days, ITeM=j, Parse=today)
 WRITE() today

ENDDO</lang>

Hy

<lang clojure>(for [x collection] (print x))</lang>

Io

<lang io>collection foreach(println)</lang>

Icon and Unicon

The example below X can be a list, string, table or other data type. <lang Icon>procedure main() X := [1,2,3,-5,6,9] every x := !L do

  write(x)

end</lang> This loop can be written somewhat more concisely as: <lang Icon>every write(!L)</lang>

J

<lang J>smoutput each i.10</lang>

Java

Works with: Java version 1.5+

<lang java>Iterable<Type> collect; ... for(Type i:collect){

  System.out.println(i);

}</lang> This works for any array type as well as any type that implements the Iterable interface (including all Collections).

Works with: Java version 1.8+

<lang java> Iterable collect; ... collect.forEach(o -> System.out.println(o)); </lang> This works with any Iterable, but not with arrays.

JavaScript

For arrays in ES5, we can use Array.forEach():

<lang JavaScript>"alpha beta gamma delta".split(' ').forEach(

 function (x) {
   console.log(x);
 }

);</lang>

Output:

alpha
beta
gamma
delta

though it will probably be more natural – dispensing with side-effects, and allowing for easier composition of nested functions – to simply use Array.map(),

<lang JavaScript>console.log("alpha beta gamma delta".split(' ').map(

 function (x) {
   return x.toUpperCase(x);
 }

).join('\n'));</lang>

Output:

ALPHA
BETA
GAMMA
DELTA

or, more flexibly, and with greater generality, obtain an accumulating fold from Array.reduce()

<lang JavaScript>console.log(

 "alpha beta gamma delta".split(' ').reduce(
   function (a, x, i, lst) {
     return lst.length - i + '. ' + x + '\n' + a;
   }, 
 )

)</lang>

Output:

1. delta
2. gamma
3. beta
4. alpha

More generally, the following works for any object, including an array. It iterates over the keys of an object. <lang JavaScript>for (var a in o) {

   print(o[a]);

}</lang> However, it has the often unwanted feature that it lists inherited properties and methods of objects as well as the ones directly set on the object -- consider whether to filter out such properties inside the loop, for example: <lang JavaScript>for (var a in o) {

   if (o.hasOwnProperty(a)) {
       print(o[a]);
   }

}</lang>

Works with: JavaScript version 1.6

Deprecated

There is also a for each in construct that iterates over the values of an object: <lang JavaScript>h = {"one":1, "two":2, "three":3} for (x in h) print(x); /* two one three

/

for each (y in h) print(y); /* 2 1 3

/</lang>

Works with: ECMAScript version 6th edition

There is also a for of construct that iterates over the values of an object: <lang JavaScript>h = {"one":1, "two":2, "three":3} for (x in h) print(x); /* two one three

/

for (y of h) print(y); /* 2 1 3

/</lang>

Jsish

Jsi supports for of for looping over element of an array. <lang javascript>for (str of "alpha beta gamma delta".split(' ')) { puts(str); }</lang>

Output:

alpha
beta
gamma
delta

Julia

Translation of: Python

<lang julia>for i in collection

  println(i)

end</lang> The Julia for statement is always a "foreach", and the built-in start:end or start:step:end "range" syntax can be used for iteration over arithmetic sequences. Many Julia objects support iteration: arrays and tuples iterate over each item, strings iterate over each character, dictionaries iterate over (key,value) pairs, numeric scalars provide a length-1 iteration over their value, and so on.

jq

Iterables:

In this section, the array defined by "example" is used as an example: <lang jq>def example: [1,2];</lang> jq has two types of iterables -- JSON arrays and JSON objects. In both cases, the ".[]" filter may be used to iterate through the values, it being understand that for objects, the "values" are the values associated with the keys: <lang jq>example | .[]

or equivalently: example[]</lang>

<lang jq>{"a":1, "b":2} | .[]

or equivalently: {"a":1, "b":2}[]</lang>

In both cases, the output is the stream consisting of the values 1 followed by 2.

Sometimes it is necessary to use an alternative to ".[]". For example, one might want to generate an index along with the array elements. In such cases, the "range(m;n)" generator, which performs a similar role to C's "for(i=m; i<n; i++)", can be used for array. Here is how range/2 would be used to perform the task for an array: <lang jq>example | . as $a | range(0; length) | $a[.]</lang> For JSON objects, the corresponding technique involves using keys, e.g. <lang jq>

{"a":1, "b":2} | . as $o | keys | map( [., $o[.]] )

</lang> produces:

[["a",1],["b",2]]

Strings:

To convert the constituent characters (or technically, codepoints) of a string into a stream of values, there are two techniques illustrated by these examples: <lang jq>"abc" | . as $s | range(0;length) | $s[.:.+1]

"abc" | explode | map( [.]|implode) | .[]</lang>

In both cases, the result is the stream of values: "a", "b", "c".

Kotlin

<lang scala>// version 1.0.6

fun main(args: Array<String>) {

   val greek = arrayOf("alpha", "beta", "gamma", "delta")
   for (letter in greek) print("$letter ")
   println()
   // or alternatively
   greek.forEach { print("$it ") }
   println()

}</lang>

Output:

alpha beta gamma delta
alpha beta gamma delta

Lasso

<lang Lasso>array(1,2,3) => foreach { stdoutnl(#1) }</lang> <lang Lasso>with i in array(1,2,3) do { stdoutnl(#i) }</lang>

K

LFE

<lang lisp>(lists:foreach

 (lambda (x)
   (io:format "item: ~p~n" (list x)))
 (lists:seq 1 10))

</lang>

LabVIEW

LabVIEW has a feature known as an Auto-Indexed Tunnel. It is the very small orange box on the lower left of the for loop.
This image is a VI Snippet, an executable image of LabVIEW code. The LabVIEW version is shown on the top-right hand corner. You can download it, then drag-and-drop it onto the LabVIEW block diagram from a file browser, and it will appear as runnable, editable code.

Lang5

LIL

<lang tcl># Loops/Foreach, in LIL set collection [list 1 2 "three"] append collection [list 4 5 six] # appended as a single item in collection print "Collection is: $collection"

using default "i" variable name set for each item

foreach $collection {print $i}

user named variable in the steps, retrieving accumulated result of loop
each loop step quotes two copies of the item

set newlist [foreach j $collection {quote $j $j}] print "Result of second foreach: $newlist"</lang>

Output:

prompt$ lil loopsForeach.lil
Collection is: 1 2 three {4 5 six}
1
2
three
4 5 six
Result of second foreach: {1 1} {2 2} {three three} {4 5 six 4 5 six}

Lingo

<lang lingo>days = ["monday", "tuesday", "wednesday", "thursday", "friday", "saturday", "sunday"] repeat with day in days

 put day

end repeat</lang> A callback-based forEach() can be implemented like this: <lang lingo>---------------------------------------- -- One of the five native iterative methods defined in ECMAScript 5 -- @param {list} tList -- @param {symbol} cbFunc -- @param {object} [cbObj=_movie]

on forEach (tList, cbFunc, cbObj)

 if voidP(cbObj) then cbObj = _movie
 cnt = tList.count
 repeat with i = 1 to cnt
   call(cbFunc, cbObj, tList[i], i, tList)
 end repeat

end</lang> <lang lingo>days = ["monday", "tuesday", "wednesday", "thursday", "friday", "saturday", "sunday"] forEach(days, #alert, _player)</lang>

Lisaac

<lang Lisaac>"Lisaac loop foreach".split.foreach { word : STRING;

 word.print;
 '\n'.print;

};</lang>

LiveCode

Livecode's for each operates on chunks which may be words, items, lines, tokens. Example is for items.<lang LiveCode>repeat for each item x in "red, green, blue"

   put x & cr
   --wait 100 millisec  -- req'd if you want to see in the LC Message Box (akin to repl)

end repeat</lang>

Logo

<lang logo>foreach [red green blue] [print ?]</lang>

Lua

Lua has 2 built-in iterators over tables.

pairs() iterates over all entries in a table, but in no particular order: <lang lua>t={monday=1, tuesday=2, wednesday=3, thursday=4, friday=5, saturday=6, sunday=0, [7]="fooday"} for key, value in pairs(t) do

 print(value, key)

end</lang> Output:

0	sunday
fooday	7
2	tuesday
3	wednesday
5	friday
4	thursday
6	saturday
1	monday

ipairs() iterates over table entries with positive integer keys, and is used to iterate over lists in order. <lang lua>l={'monday', 'tuesday', 'wednesday', 'thursday', 'friday', 'saturday', 'sunday', not_a_number='fooday', [0]='today', [-1]='yesterday' } for key, value in ipairs(l) do

 print(key, value)

end</lang> Output:

1	monday
2	tuesday
3	wednesday
4	thursday
5	friday
6	saturday
7	sunday

Note that ipairs() ignores non-numeric and non-positive integer keys.

M2000 Interpreter

Iterators we have for Arrays, Inventories and Stacks (containers). Each(object Start to End), or Each(object 1 to -1) or Each(Object, 1,-1). We can use -2 for second from end item. We can use step inside while iterator {} using Iterator=Each(object, new_start, end_item). We can read cursor using ^. So Print k^, k2^, k1^ return positions (from 0 for inventories). We can use more than one iterators for an object.

<lang M2000 Interpreter> Module Checkit {

     \\ Inventories may have keys or keys/values
     \\ here keys are values too
     Inventory Alfa="Apple", "Banana", "Coconut"
     \\ key 30 has value 25, other keys have value same as key.
     Inventory Beta=100, 30:=25, 20, 5
     Print "Parallel"
     k=Each(Alfa)
     k1=Each(Alfa End to Start)
     k2=Each(Beta)
     \\ Parallel iterators
     \\ when one of them end then while end too.
     \\ so 5 not printed. Print 100, 25, 20
     While k,k2, k1 {
           Print Eval$(k), Eval$(k1), Eval(k2)
     }
     Print "Nested"
     \\ Nested iterators
     k=Each(Alfa)
     While k {
     k1=Each(Alfa End to Start)
           While k1 {
                 Print Eval$(k), Eval$(k1)
           }
     }

} Checkit </lang>

Maple

<lang Maple> for p in [2, 3, 5, 7] do

   print(p);

end do; </lang>

Mathematica

Foreach over list of strings <lang mathematica>s = (StringSplit@Import["ExampleData/USConstitution.txt"])1;;7; Do[

Print@i,
{i, s}

]</lang> Output:

We
the
People
of
the
United
States,

MATLAB / Octave

<lang Matlab> list1 = [1,5,6,7,-7,-9];

   for k = list1,    % list1 must be a row vector (i.e. array of size 1xn)
       printf('%i\n',k)
   end; </lang>

<lang Matlab> list2 = {'AA','BB','CC'};

   for k = list2,    % list2 must be a row vector (i.e. array of size 1xn)
       printf('%s\n',k{1})
   end; </lang>

A vectorized version of the code is <lang Matlab> printf('%d\n',list1);

 printf('%s\n',list2{:});  </lang>

Maxima

<lang maxima>for n in [2, 3, 5, 7] do print(n);</lang>

MAXScript

<lang maxscript> arr = for i in 1 to 50 collect ("Number: " + (random 10 99) as string) makeuniquearray arr sort arr

for i in arr do print i as string </lang>

Metafont

If we have a list of arbitrary items, we can simply use for: <lang metafont>for x = "mary", "had", "a", "little", "lamb": message x; endfor end</lang> The list can be generated in place by any suitable macro or another loop... e.g. let us suppose we have things like a[n] defined (with maximum n being 10). Then <lang metafont>for x = for i = 1 upto 9: a[i], endfor, a[10]: show x; endfor end</lang> works more like a foreach; we could make a macro to hide the strangeness of such a code.

min

Works with: min version 0.19.3

<lang min>(1 2 3) 'puts foreach</lang>

MiniScript

<lang MiniScript>for i in collection

  print i

end</lang> The MiniScript for statement is always a "foreach", and the standard range intrinsic can be used for iteration over arithmetic sequences. All MiniScript collection types support iteration: lists iterate over each item, strings iterate over each character, and maps/objects iterate over (key,value) pairs.

MOO

<lang moo>things = {"Apple", "Banana", "Coconut"};

for thing in (things)

   player:tell(thing);

endfor</lang>

Nemerle

This works on anything which implements the IEnumerable interface. <lang Nemerle>def things = ["Apple", "Banana", "Coconut"];

foreach (thing in things) WriteLine(thing.ToLower()); foreach (i in [5, 10 .. 100]) Write($"$i\t");</lang>

NetRexx

<lang NetRexx>/* NetRexx */ options replace format comments java crossref savelog symbols nobinary

 say
 say 'Loops/Foreach'

 days = ['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday']
 daysl = Arrays.asList(days)
 daysi = daysl.iterator

 loop while daysi.hasNext
   say daysi.next
   end</lang>

NewLISP

<lang NewLISP>(map println '(Apple Banana Coconut))</lang>

Nim

<lang nim>var list: seq[string] = @[] list.add("lorem") list.add("ipsum") list.add("dolor") for i in items(list):

 echo(i)</lang>

Output:

lorem
ipsum
dolor

Objective-C

Works with: Objective-C version 2.0+

Works with: GNUstep

Works with: Cocoa

<lang objc>NSArray *collect; //... for(Type i in collect){

  NSLog(@"%@", i);

}</lang> collect can be any object that adopts the NSFastEnumeration protocol.

Or (always using OpenStep compatible frameworks):

Works with: Objective-C version <2.0

<lang objc>NSArray *collect; //... NSEnumerator *enm = [collect objectEnumerator]; id i; while( (i = [enm nextObject]) ) {

 // do something with object i

}</lang>

Objeck

<lang objeck>fruits := ["Apple", "Banana", "Coconut"]; each(i : fruits) {

 fruits[i]->PrintLine();

};</lang>

OCaml

List of integers: <lang ocaml>List.iter

 (fun i -> Printf.printf "%d\n" i)
 collect_list</lang>

Array of integers: <lang ocaml>Array.iter

 (fun i -> Printf.printf "%d\n" i)
 collect_array</lang>

Oforth

<lang Oforth>: printMonths | m | Date.Months forEach: m [ m . ] ;</lang>

But, apply can be used instead of a loop : <lang Oforth>#. Date.Months apply</lang>

Octave

<lang octave>a = [ 1,4,3,2 ]; b = [ 1,2,3,4; 5,6,7,8 ]; for v = a

 disp(v); % output single values: 1,4,3,2

endfor for v = b

 disp(v); % v is the column vector [1;5], then [2;6] ...

endfor</lang> We can also iterate over structures: <lang octave>x.a = [ 10, 11, 12 ]; x.b = { "Cell", "ul", "ar" }; for [ val, key ] = x

 disp(key);
 disp(val);

endfor</lang>

Ol

<lang scheme> (for-each print '(1 3 4 2)) (print) (for-each (lambda (a b c) (print a "-" b "/" c))

  '(1 2 3 4)
  '(5 6 7 8)
  '(a b x z))

</lang>

Output:

1
3
4
2

1-5/a
2-6/b
3-7/x
4-8/z

ooRexx

The OVER loop control keyword is used to select each item in a collection in turn. Open Object Rexx allows the DO block structure keyword to be used to start a loop for backward compatibility with classic Rexx; the LOOP keyword is preferred here as it is self-documenting. <lang ooRexx>/* Rexx */ say say 'Loops/Foreach' out =

days = .array~of('Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday')

loop daysi over days

 out ||= daysi' '
 end daysi

say out~strip()

exit</lang> Output:

Loops/Foreach
Sunday Monday Tuesday Wednesday Thursday Friday Saturday

Oz

<lang oz>declare

 MyList = [1 2 3 4]

in

 {ForAll MyList Show}

 %% or:
 for E in MyList do {Show E} end</lang>

PARI/GP

<lang parigp>for(i=1,#v,print(v[i]))</lang>

or (PARI/GP >= 2.4)

<lang parigp>apply(x->print(x),v)</lang>

Pascal

See Delphi

Perl

<lang perl>foreach my $i (@collection) {

  print "$i\n";

}</lang> The keyword for can be used instead of foreach. If a loop variable (here $i) is not given, then $_ is used.

A more compact notation using perl statement modifier: <lang perl>print "$_\n" foreach @collection</lang>

In perl, it is possible to loop against an explicit list, so there is no need to define a container:

<lang perl>foreach $l ( "apples", "bananas", "cherries" ) {

 print "I like $l\n";

}</lang>

Perl 6

Works with: Rakudo version 2015.10-40

<lang perl6>say $_ for @collection;</lang> Perl 6 leaves off the each from foreach, leaving us with for instead. The variable $_ refers to the current element, unless you assign a name to it using ->. <lang perl6>for @collection -> $currentElement { say $currentElement; }</lang> Perl 6 will do it's best to put the topic at the right spot. <lang perl6>.say for @collection; for @collection { .say };</lang> Iteration can also be done with hyperoperators. In this case it's a candidate for autothreading and as such, execution order may vary. The resulting list will be in order. <lang per6>@collection>>.say; @collection>>.=&infix:<+>(2); # increment each element by 2</lang>

Phix

<lang Phix>sequence s = {-2,"field",3.14159268979,{"this","that"}} for i=1 to length(s) do

   ?s[i]

end for</lang>

PHL

<lang phl>var numbers = 1..10;

numbers each # (number) [

   printf("%i\n", number);

];</lang>

PHP

<lang php>foreach ($collect as $i) {

  echo "$i\n";

}

foreach ($collect as $key => $i) {

  echo "\$collect[$key] = $i\n";

}</lang> foreach can also iterate over objects. By default it iterates over all visible fields of an object.

PicoLisp

<lang PicoLisp>(mapc println '(Apple Banana Coconut))</lang>

Pike

<lang pike>int main(){

  array(int|string) collect = ({109, "Hi", "asdf", "qwerty"});
  foreach(collect, int|string elem){
     write(elem + "\n");
  }

}</lang> Iterating over the keys and values of a mapping (dictionary): <lang pike>int main(){

   mapping(string:string) coll = (["foo":"asdf", "bar":"qwer", "quux":"zxcv"]);
   foreach (coll;string key;string val)
       write(key+" --> "+val+"\n");
   }

}</lang>

PL/I

<lang pli>declare A(10) fixed binary; do i = lbound(A,1) to hbound(A,1);

  put skip list (A(i));

end;</lang>

Pop11

Iteration over list: <lang pop11>lvars el, lst = [1 2 3 4 foo bar]; for el in lst do

  printf(el,'%p\n');

endfor;</lang>

PostScript

The forall operator performs a loop over a collection (array, string or dictionary). Strings and arrays can be treated very much the same: <lang postscript>[1 5 3 2] { = } forall (abc) { = } forall</lang> but dictionaries take a little more work since a key/value pair is pushed on the stack in each iteration: <lang postscript><</a 25 /b 42>> {

 exch (Key: ) print
 =
 (Value: ) print
 =

} forall</lang>

PowerShell

<lang PowerShell> $colors = "Black","Blue","Cyan","Gray","Green","Magenta","Red","White","Yellow",

         "DarkBlue","DarkCyan","DarkGray","DarkGreen","DarkMagenta","DarkRed","DarkYellow"

foreach ($color in $colors) {

   Write-Host "$color" -ForegroundColor $color

} </lang>

Output:

Black
Blue
Cyan
Gray
Green
Magenta
Red
White
Yellow
DarkBlue
DarkCyan
DarkGray
DarkGreen
DarkMagenta
DarkRed
DarkYellow

Prolog

For example : <lang Prolog>?- foreach(member(X, [red,green,blue,black,white]), writeln(X)). red green blue black white true. </lang>

Python

<lang python>for i in collection:

  print i</lang>

Note: The Python for statement is always a "foreach" ... and the range() and xrange() built-in functions are used to generate lists of indexes over which it will iterate as necessary. The majority of Python objects support iteration. Lists and tuples iterate over each item, strings iterate over each character, dictionaries iterate over keys, files iterate over lines, and so on.

For example: <lang python>lines = words = characters = 0 f = open('somefile','r') for eachline in f:

   lines += 1
   for eachword in eachline.split():
       words += 1
       for eachchar in eachword:
           characters += 1

print lines, words, characters</lang>

Whether for loops over the elements of the collection in order depends on the collection having an inherent order or not. Elements of strings (i.e. characters), tuples and lists, for example, are ordered but the order of elements in dictionaries and sets is not defined.

One can loop over the key/value pairs of a dictionary in alphabetic or numeric key order by sorting the sequence of keys, provided that the keys are all of comparable types. In Python 3.x a sequence of mixed numeric and string elements is not sortable (at least not with the default invocation of sorted()), whereas in Python 2.x numeric types are sorted according to their string representation by default:

<lang python>d = {3: "Earth", 1: "Mercury", 4: "Mars", 2: "Venus"} for k in sorted(d):

   print("%i: %s" % (k, d[k]))

d = {"London": "United Kingdom", "Berlin": "Germany", "Rome": "Italy", "Paris": "France"} for k in sorted(d):

   print("%s: %s" % (k, d[k]))</lang>

Works with: Python version 2.x

<lang python>d = {"fortytwo": 42, 3.14159: "pi", 23: "twentythree", "zero": 0, 13: "thirteen"} for k in sorted(d):

   print("%s: %s" % (k, d[k]))</lang>

R

Racket

lang racket

an example sequence

(define sequence '("something" 1 2 "foo"))

works for any sequence

(for ([i sequence])

 (displayln i))

</lang>

REBOL

<lang REBOL>REBOL [ Title: "Loop/Foreach" URL: http://rosettacode.org/wiki/Loop/Foreach ]

x: [Sork Gun Blues Neds Thirst Fright Catur]

foreach i x [prin rejoin [i "day "]] print ""

REBOL also has the 'forall' construct, which provides the rest of
the list from the current position.

forall x [prin rejoin [x/1 "day "]] print ""</lang> Output:

Sorkday Gunday Bluesday Nedsday Thirstday Frightday Caturday
Sorkday Gunday Bluesday Nedsday Thirstday Frightday Caturday

Red

<lang Red>>> blk: ["John" 23 "dave" 30 "bob" 20 "Jeff" 40] >> foreach item blk [print item] John 23 dave 30 bob 20 Jeff 40 >> foreach [name age] blk [print [name "is" age "years old"]] John is 23 years old dave is 30 years old bob is 20 years old Jeff is 40 years old

>> forall blk [print blk] John 23 dave 30 bob 20 Jeff 40 23 dave 30 bob 20 Jeff 40 dave 30 bob 20 Jeff 40 30 bob 20 Jeff 40 bob 20 Jeff 40 20 Jeff 40 Jeff 40 40</lang>

Retro

Retro has for-each combinators for operating on elements of various data structures.

<lang Retro># Strings

This will display the ASCII code for each character in a string

~~~ 'This_is_a_message [ n:put sp ] s:for-each ~~~

Array

Display each element

~~~ { #1 #2 #3 } [ n:put sp ] a:for-each ~~~

Linked List

Using the dictionary as an example, display each name

~~~ &Dictionary [ d:name s:put sp ] d:for-each ~~~ </lang>

REXX

<lang rexx>days = 'zuntik montik dinstik mitvokh donershtik fraytik shabes'

 do j=1  for words(days)              /*loop through days of the week. */
 say word(days,j)                     /*display the weekday to screen. */
 end   /*j*/                        
                                      /*stick a fork in it, we're done.*/</lang>

Ring

<lang ring> aList = "Welcome to the Ring Programming Language" for n in aList

   see n + nl

next </lang>

Ruby

<lang ruby>for i in collection do

 puts i

end</lang> This is syntactic sugar for: <lang ruby>collection.each do |i|

 puts i

end</lang> There are various flavours of each that may be class-dependent: String#each_char, Array#each_index, Hash#each_key, etc

Rust

Rust's for-loop already is a foreach-loop. <lang rust>let collection = vec![1,2,3,4,5]; for elem in collection {

   println!("{}", elem);

}</lang>

Do note that Rust moves values by default and doesn't copy them. A vector would be unusable after looping over it like above. To preserve it, borrow it or use an Iter, to mutate values do a mutable borrow or create an IterMut. To get an immutable reference omit the mut-part. <lang rust>let mut collection = vec![1,2,3,4,5]; for mut_ref in &mut collection { // alternatively: // for mut_ref in collection.iter_mut() {

   *mut_ref *= 2;
   println!("{}", *mut_ref);

}

// immutable borrow for immut_ref in &collection { // alternatively: // for immut_ref in collection.iter() {

   println!("{}", *immut_ref);

}</lang>

Since Rust 1.21 foreach can be used explicitly executing a closure on each element. <lang rust>let collection = vec![1, 2, 3, 4, 5]; collection.iter().for_each(|elem| println!("{}", elem));</lang>

Salmon

<lang Salmon>iterate (x; ["Red", "Green", "Blue"])

   x!;</lang>

output:

Red
Green
Blue

SAS

<lang sas>/* Initialize an array with integers 1 to 10, and print their sum */ data _null_; array a a1-a10; n=1; do over a;

 a=n;
 n=n+1;

end; s=sum(of a{*}); put s; run;</lang>

Sather

<lang sather>class MAIN is

 main is
    num:ARRAY{INT} := |1, 5, 4, 3, 10|;
    loop
      -- the iterator elt! behaves like a "foreach",
      -- yielding the next element of the array at each iteration
      #OUT + num.elt! + "\n";
    end;
 end;

end;</lang>

Scala

<lang scala>val collection = Array(1, 2, 3, 4) collection.foreach(println)</lang> Alternatively: <lang scala>(element <- 1 to 4).foreach(println)</lang>

Scheme

List: <lang scheme>(for-each

 (lambda (i) (display i) (newline))
 the_list)</lang>

Scilab

Works with: Scilab version 5.5.1

<lang>for e=["a","b","c"]

   printf("%s\n",e)

end</lang>

Output:

a
b
c

Seed7

The for loop of Seed7 can be used to loop over the elements of a container. <lang seed7>$ include "seed7_05.s7i";

var array string: things is [] ("Apple", "Banana", "Coconut");

const proc: main is func

 local
   var string: thing is "";
 begin
   for thing range things do
     writeln(thing);
   end for;
 end func;</lang>

Self

<lang self>aCollection do: [| :element | element printLine ].</lang> (Provided that the objects in the collection understand the printLine method).

SETL

<lang setl>S := {1,2,3,5,8,13,21,34,55,89}; for e in S loop

   print(e);

end loop;</lang>

Sidef

foreach loop: <lang ruby>foreach [1,2,3] { |i|

   say i

}</lang>

for-in loop: <lang ruby>for i in [1,2,3] {

   say i

}</lang>

.each method: <lang ruby>[1,2,3].each { |i|

   say i

}</lang>

Slate

<lang slate>c do: [| :obj | print: obj].</lang>

Smalltalk

<lang smalltalk>aCollection do: [ :element | element displayNl ].</lang> (Provided that the objects in the collection understand the displayNl method).

Snabel

Prints foo, bar & baz followed by newlines. <lang snabel>['foo' 'bar' 'baz'] &say for</lang>

Sparkling

Sparkling currently has no "foreach" construct, but there's a "foreach" function in the standard library:

<lang sparkling>let hash = { "foo": 42, "bar": 1337, "baz": "qux" }; foreach(hash, function(key, val) {

   print(key, " -> ", val);

});</lang>

Standard ML

List of integers: <lang sml>app

 (fn i => print (Int.toString i ^ "\n"))
 collect_list</lang>

Array of integers: <lang sml>Array.app

 (fn i => print (Int.toString i ^ "\n"))
 collect_array</lang>

Stata

<lang stata>local a 2 9 4 7 5 3 6 1 8 foreach i in `a' { display "`i'" }</lang>

Suneido

<lang Suneido>for i in #(1, 2, 3)

   Print(i)</lang>

Swift

<lang swift>for i in [1,2,3] {

  print(i)

}</lang> This works for any type that conforms to the SequenceType protocol (including arrays, collections, generators, ranges).

Alternately:

Works with: Swift version 2.x+

<lang swift>[1,2,3].forEach {

  print($0)

}</lang>

SystemVerilog

<lang SystemVerilog>program main;

 int values[$];

 initial begin
   values = '{ 1, 3, 7, 11 };
   foreach (values[i]) begin
      $display( "%0d --> %0d", i, values[i] );
   end
 end

endprogram</lang>

Tcl

<lang tcl>foreach i {foo bar baz} {

   puts "$i"

}</lang> Note that foreach also accepts multiple variables: <lang tcl>foreach {x y} {1 2 3 4} {

   puts "$x,$y"

}</lang> And also multiple lists: <lang tcl>foreach i {1 2 3} j {a b c} {

   puts "$i,$j"

}</lang> Or any combination of variables/list: <lang tcl>foreach i {1 2 3} {x y} {a b c d e f} {

   puts "$i,$x,$y"

}</lang>

Trith

<lang trith>[1 2 3 4 5] [print] each</lang>

TUSCRIPT

<lang tuscript>$$ MODE TUSCRIPT week="Monday'Tuesday'Wednesday'Thursday'Friday'Saterday'Sunday" LOOP day=week PRINT day ENDLOOP</lang> Output:

Monday
Tuesday
Wednesday
Thursday
Friday
Saterday
Sunday

UNIX Shell

To iterate any single list, you use a for loop.

Works with: Bourne Shell

<lang bash>for file in *.sh; do

 echo "filename is $file"

done</lang> If the list is in a shell parameter (like PATH), you adjust IFS.

Works with: Bourne Shell

<lang bash>PATH=/usr/bin:/bin:/usr/sbin:/sbin:/usr/X11R6/bin:/usr/local/bin

oldifs=$IFS IFS=: for dir in $PATH; do

 echo search $dir

done IFS=$oldifs</lang> Some shells have real arrays. The for loop can also iterate these.

Works with: Bash

<lang bash>collection=("first" "second" "third" "fourth" "something else") for x in "${collection[@]}"; do

 echo "$x"

done</lang>

Works with: pdksh version 5.2.14

<lang bash>set -A collection "first" "second" "third" "fourth" "something else" for x in "${collection[@]}"; do

 echo "$x"

done</lang>

C Shell

<lang csh>set collection=(first second third fourth "something else") foreach x ($collection:q) echo $x:q end</lang>

V

Vala

<lang vala>List<string> things = new List<string> (); things.append("Apple"); things.append("Banana"); things.append("Coconut");

foreach (string thing in things) {

 stdout.printf("%s\n", thing);

}</lang>

Vim Script

Vim Script's for-loop is actually a foreach-loop and iterates through a list. <lang vim>for i in ["alpha", "beta", 42, 5.54]

   echo i

endfor</lang>

Wart

<lang wart>each x '(1 2 3)

 prn x</lang>

WDTE

<lang WDTE>let a => import 'arrays'; let s => import 'stream';

a.stream [5; 7; 3] -> s.map (io.writeln io.stdout) -> s.drain

</lang>

XLISP

XLISP's FOR-EACH applies a procedure to each member of a list in turn. <lang lisp>(FOR-EACH PRINT '(CYRUS CAMBYSES DARIUS XERXES ARTAXERXES))</lang>

Output:

CYRUS 
CAMBYSES 
DARIUS 
XERXES 
ARTAXERXES

XPL0

Translation of C example: <lang XPL0>include c:\cxpl\codes; int List, I; [List:= ["Red", "Green", "Blue", "Black", "White"]; for I:= 0, 5-1 do

       [Text(0, List(I));  CrLf(0)];

]</lang>

XSLT

For-each is the only iteration construct that is built into XSLT. All other iteration is either implied by applying a template to all members matching an XPath expression, or built from recursive application of a template. You have access to something like a loop counter with the one-based "position()" function. <lang xml><fo:block font-weight="bold">Adults:</fo:block> <xsl:for-each select="person[@age >= 21]">

 <fo:block><xsl:value-of select="position()"/>. <xsl:value-of select="@name"/></fo:block>

</xsl:for-each></lang>

zig

<lang zig>const warn = @import("std").debug.warn;

pub fn main() void {

   const items = []i16{ 0, 1, 1, 2, 3, 5, 8 };

   for (items) |i| {
       warn("{}\n", i);
   }

}</lang>

zkl

Translation of: XPL0

<lang zkl>foreach c in (T("Red","Green","Blue","Black","White"))

 { print(c," "); }</lang>

Output:

Red Green Blue Black White

Other forms of foreach, one that breaks apart a container into elements and one line nested loops. <lang zkl>foreach x,y,z in (T(T(1,2,3), T(4,5,6))) { println(x,y,z) } foreach x,y,z in (T(1,2,3), T(4,5), T(6)){ println(x,y,z) }</lang>

Output:

123
456

Revision as of 00:18, 31 October 2019

arrays

doubly linked lists

vectors

strings

vectors

maps

integers

Objects

Coroutines

Files

Enumerations

Boolean expression variant

Icon and Unicon

MATLAB / Octave