Loops/Foreach

From Rosetta Code
Task
Loops/Foreach
You are encouraged to solve this task according to the task description, using any language you may know.

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



11l[edit]

Translation of: C#
V things = [‘Apple’, ‘Banana’, ‘Coconut’]

L(thing) things
   print(thing)

ACL2[edit]

(defun print-list (xs)
   (if (endp xs)
       nil
       (prog2$ (cw "~x0~%" (first xs))
               (print-list (rest xs)))))
> (print-list (list 1 "a" 1/2 (list 1 2) 'sym))
1
"a"
1/2
(1 2)
SYM
NIL

Action![edit]

In Action! there is no for-each loop.

PROC Main()
  DEFINE PTR="CARD"
  BYTE i
  PTR ARRAY items(10)
  items(0)="First"   items(1)="Second"
  items(2)="Third"   items(3)="Fourth"
  items(4)="Fifth"   items(5)="Sixth"
  items(6)="Seventh" items(7)="Eighth"
  items(8)="Ninth"   items(9)="Tenth"

  PrintE("In Action! there is no for-each loop")
  PutE()
  FOR i=0 TO 9
  DO
    PrintE(items(i))
  OD
RETURN
Output:

Screenshot from Atari 8-bit computer

In Action! there is no for-each loop

First
Second
Third
Fourth
Fifth
Sixth
Seventh
Eighth
Ninth
Tenth

Ada[edit]

arrays[edit]

with Ada.Integer_Text_IO;
use  Ada.Integer_Text_IO;

procedure For_Each is

   A : array (1..5) of Integer := (-1, 0, 1, 2, 3);

begin

   for Num in A'Range loop
      Put( A (Num) );
   end loop;

end For_Each;

Alternative solution (Ada 2012):

   for Item of A loop
      Put( Item );
   end loop;

doubly linked lists[edit]

Works with: Ada 2005
with Ada.Integer_Text_IO, Ada.Containers.Doubly_Linked_Lists;
use  Ada.Integer_Text_IO, Ada.Containers;

procedure Doubly_Linked_List is

   package DL_List_Pkg is new Doubly_Linked_Lists (Integer);
   use     DL_List_Pkg;

   procedure Print_Node (Position : Cursor) is
   begin
      Put (Element (Position));
   end Print_Node;
   
   DL_List : List;
   
begin
   
   DL_List.Append (1);
   DL_List.Append (2);
   DL_List.Append (3);
   
   -- Iterates through every node of the list.
   DL_List.Iterate (Print_Node'Access);
   
end Doubly_Linked_List;

vectors[edit]

Works with: Ada 2005
with Ada.Integer_Text_IO, Ada.Containers.Vectors;
use  Ada.Integer_Text_IO, Ada.Containers;

procedure Vector_Example is

   package Vector_Pkg is new Vectors (Natural, Integer);
   use     Vector_Pkg;

   procedure Print_Element (Position : Cursor) is
   begin
      Put (Element (Position));
   end Print_Element;
   
   V : Vector;
   
begin
   
   V.Append (1);
   V.Append (2);
   V.Append (3);
      
   -- Iterates through every element of the vector.
   V.Iterate (Print_Element'Access);
   
end Vector_Example;

Aikido[edit]

Aikido's foreach loop allows iteration through multiple value types.

strings[edit]

var str = "hello world"
foreach ch str {    // you can also use an optional 'in'
    println (ch)   // one character at a time
}

vectors[edit]

var vec = [1,2,3,4]
foreach v vec {    // you can also use an optional 'in'
    println (v)
}

maps[edit]

var cities = {"San Ramon": 50000, "Walnut Creek": 70000, "San Francisco": 700000}   // map literal
foreach city cities {
    println (city.first + " has population " + city.second)
}

integers[edit]

foreach i 100 {
    println (i)    // prints values 0..99
}

foreach i 10..20 {
    println (i)     // prints values 10..20
}

var a = 20
var b = 10
foreach i a..b {
    println (i)   // prints values from a to b (20..10)
}

Objects[edit]

Aikido allows definition of a foreach operator for an object. In this example we define a single linked list and a foreach operator to iterate through it

class List {
    class Element (public data) {
        public var next = null
    }
    var start = null

    public function insert (data) {
        var element = new Element (data)
        element.next = start
        start = element
    }

    public operator foreach (var iter) {
        if (typeof(iter) == "none") {   // first iteration
            iter = start
            return iter.data
        } elif (iter.next == null) {    // check for last iteration
            iter = none
        } else {
            iter = iter.next      // somewhere in the middle
            return iter.data
        }
    }

}

var list = new List()
list.insert (1)
list.insert (2)
list.insert (4)

foreach n list {
    println (n)
}

Coroutines[edit]

Aikido supports coroutines. The foreach operator may be used to iterate thorough the generated values.

// 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)
}

Files[edit]

If you open a file you can iterate through all the lines

var s = openin ("input.txt")
foreach line s {
    print (line)
}

Enumerations[edit]

enum Color { 
   RED, GREEN, BLUE
}

foreach color Color {
    println (color)
}

Aime[edit]

# iterate over a list of integers
integer i, v;

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

ALGOL 68[edit]

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
[]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

Output:

Mary Had          +1 little lamb.


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

ALGOL 68RS and Algol68toc have a FORALL loop, the following is equivalent to the example above:

FORALL index IN collection DO
  print((collection[index]," "))
OD

AmigaE[edit]

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

Apex[edit]

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

for (Integer i : myInts) {
    System.debug(i);
}

AppleScript[edit]

repeat with fruit in {"Apple", "Orange", "Banana"}
  log contents of fruit
end repeat

Arturo[edit]

arr: ["one" "two" "three"]

dict: #[	
    name:		"John"
	surname:	"Doe"
	age:		34
]

loop arr 'item ->
    print item

loop dict [key val]->
    print [key "=>" val]
Output:
one
two
three
name => John 
surname => Doe 
age => 34

AutoHotkey[edit]

string = mary,had,a,little,lamb
Loop, Parse, string, `,  
  MsgBox %A_LoopField%

AWK[edit]

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).

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

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:

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

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:

# This will not work
BEGIN {
  for (el in "apples","bananas","cherries") {
    print "I like " el
  }
}

BASIC[edit]

BaCon[edit]

BaCon includes support for delimited strings. Delimited strings form a type of collection. Along with this support is a for in loop. Not quite a for each but pretty close.

OPTION COLLAPSE TRUE
FOR x$ IN "Hello cruel world"
    PRINT x$
NEXT

FOR y$ IN "1,2,\"3,4\",5" STEP ","
    PRINT y$
NEXT
Output:
prompt$ bacon -q forin.bac >/dev/null
prompt$ ./forin
Hello
cruel
world
1
2
"3,4"
5

The OPTION COLLAPSE TRUE statements prevents empty results when multiple delimiters appear together. The default delimiter is space, and can be changed with OPTION DELIM x where x is a static string literal.

BASIC256[edit]

BASIC-256 does not have a FOR EACH type statement. Use a FOR loop to iterate through an array by index.

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

Output:

The quick brown fox jumps over the lazy dog.

BBC BASIC[edit]

      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

Commodore BASIC[edit]

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

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.

Creative Basic[edit]

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

FreeBASIC[edit]

' 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; " ";
Next

Print
Sleep
Output:
 1  2  3  4  5  6  7  8  9  10  11

Gambas[edit]

Click this link to run this code

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;;
Next

End
Output:
0 1 2 3 4 5 6 7 8 9

IS-BASIC[edit]

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.

IWBASIC[edit]

Linked List

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   
NEXT

PRINT

'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

An Array

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

Lambdatalk[edit]

{def collection alpha beta gamma delta} 
-> collection

{S.map {lambda {:i} {br}:i} {collection}} 
->
alpha 
beta 
gamma 
delta

or

{def S.foreach
 {lambda {:s}
  {if {S.empty? {S.rest :s}}
   then {S.first :s}
   else {S.first :s} {br}{S.foreach {S.rest :s}}}}}

{S.foreach {collection}}
->
alpha 
beta 
gamma 
delta

Liberty BASIC[edit]

The most natural way is to use a csv list with a sentinel value.

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

NS-HUBASIC[edit]

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.

PureBasic[edit]

Works for LinkedLists and Maps

ForEach element()
  PrintN(element())
Next

Run BASIC[edit]

t$={Sunday,Monday,Tuesday,Wednesday,Thursday,Friday,Saturday"

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

TI-89 BASIC[edit]

Local i,strs
Define strs = {"Lorem","ipsum","dolor"}
For i, 1, dim(strs)
  Disp strs[i]
EndFor

VBA[edit]

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

VBScript[edit]

items = Array("Apple", "Orange", "Banana")

For Each x In items
    WScript.Echo x
Next

Visual Basic .NET[edit]

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


Yabasic[edit]

//Yabasic tampoco tiene una construcción ForEach. 
//Mediante un bucle FOR iteramos a través de una matriz por índice. 
//READ-DATA se usa para rellenar la matriz

dim arreglo(10)
data 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11
for each = 0 to arraysize(a(),1)
    read arreglo(each)
next each

for each = 0 to arraysize(a(),1)
    print arreglo(each), " ";
next each
print
end


Batch File[edit]

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

Direct usage:

@echo off
for %%A in (This is a sample collection) do (
     echo %%A
)

Using a Collection Variable:

@echo off
set "collection=This is a sample collection"
for %%A in (%collection%) do (
     echo %%A
)
They have the Same Output:
This
is
a
sample
collection

bc[edit]

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.

a[0] = .123
a[1] = 234
a[3] = 95.6
for (i = 0; i < 4; i++) {
    a[i]
}

Bracmat[edit]

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:

  ( list
  =   Afrikaans
      Ελληνικά
      עברית
      മലയാളം
      ئۇيغۇرچە
  )

The 'while' solution. Use an auxiliary variable L that gets its head chopped off until nothing is left:

  !list:?L
& whl'(!L:%?language ?L&out$!language)

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.

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

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.

  (   !list
    : ? (%@?language&out$!language&~) ?
  | 
  )

C[edit]

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.

#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]);
}

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

#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);
}

C int array as a collection of int (array size known at compile-time)

#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);
}

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);
}

C#[edit]

string[] things = {"Apple", "Banana", "Coconut"};

foreach (string thing in things)
{
    Console.WriteLine(thing);
}

C++[edit]

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.

for (container_type::iterator i = container.begin(); i != container.end(); ++i)
{
  std::cout << *i << "\n";
}

However the idiomatic way to output a container would be

std::copy(container.begin(), container.end(),
          std::ostream_iterator<container_type::value_type>(std::cout, "\n"));

There's also an algorithm named for_each. However, you need a function or function object to use it, e.g.

void print_element(container_type::value_type const& v)
{
  std::cout << v << "\n";
}

...
  std::for_each(container.begin(), container.end(), print_element);
Works with: C++11
for (auto element: container)
{
  std::cout << element << "\n";
}

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:

for (auto const& element: container)
{
  std::cout << element << "\n";
}

Of course the container elements can also be changed by using a non-const reference (provided the container isn't itself constant):

for (auto&& element: container) //use a 'universal reference'
{
  element += 42;
}

Chapel[edit]

var food = ["Milk", "Bread", "Butter"];
for f in food do writeln(f);

Clojure[edit]

(doseq [item collection] (println item))

CLU[edit]

As in Python (which no doubt got the idea from CLU), every for loop in CLU is really a foreach, and iterating over a range of numbers is done by using an iterator (e.g. int$from_to).

Unlike Python, the for loop only accepts iterators, and collections are not automatically cast into iterators. To loop over the elements of an array, one needs to explicitly use the elements iterator.

start_up = proc ()
    po: stream := stream$primary_output()
    
    words: array[string] := array[string]$
        ["enemy", "lasagna", "robust", "below", "wax"]
    
    for word: string in array[string]$elements(words) do
        stream$putl(po, word)
    end
end start_up

CMake[edit]

set(list one.c two.c three.c)

foreach(file ${list})
  message(${file})
endforeach(file)

COBOL[edit]

The following is in the Managed COBOL dialect:

Translation of: C#
Works with: Visual COBOL
01  things occurs 3.
...
set content of things to ("Apple", "Banana", "Coconut")
perform varying thing as string through things
    display thing
end-perform

ColdFusion[edit]

<Cfloop list="Fee, Fi, Foe, Fum" index="i">
  <Cfoutput>#i#!</Cfoutput>
</Cfloop>

Common Lisp[edit]

(loop for i in list do (print i))

or

(map nil #'print list)

or

(dolist (x the-list) (print x))

or

(use-package :iterate)
(iter
  (for x in the-list)
  (print x))

Using DO[edit]

(let ((the-list '(1 7 "foo" 1 4)))	; Set the-list as the list
  (do ((i the-list (rest i)))		; Initialize to the-list and set to rest on every loop
      ((null i))			; Break condition
    (print (first i))))	                ; On every loop print list's first element
Output:
1 
7 
"foo" 
1 
4 

D[edit]

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.

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);        
}
Output:
A
B
C
A
B
C
10
20
30
1 10
2 20
3 30

Dao[edit]

items = { 1, 2, 3 }
for( item in items ) io.writeln( item )

Delphi[edit]

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().

program LoopForEach;

{$APPTYPE CONSOLE}

var
  s: string;
begin
  for s in 'Hello' do
    Writeln(s);
end.

Output:

H
e
l
l
o

Dragon[edit]

for value : array {
   showln value
}

Dyalect[edit]

for i in [1,2,3] {
   print(i)
}

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:

for i in [1,2,3].Iterate() {
   print(i)
}

This would perfectly work with any custom iterator as well:

func myCollection() {
    yield 1
    yield 2
    yield 3
}

for i in myCollection() {
   print(i)
}

All three code samples would output:

1
2
3

E[edit]

for e in theCollection {
    println(e)
}

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

EchoLisp[edit]

(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, ...

Ecstasy[edit]

module LoopForEach
    {
    @Inject Console console;
    void run()
        {
        val vals = [10, 20, 30, 40];
        console.println("Array of values:");
        Loop: for (val val : vals)
            {
            console.println($"  value #{Loop.count + 1}: {val}");
            }

        Map<String, Int> pairs = ["x"=42, "y"=69];
        console.println("\nKeys and values:");
        for ((String key, Int val) : pairs)
            {
            console.println($"  {key}={val}");
            }
        console.println("\nJust the keys:");
        Loop: for (String key : pairs)
            {
            console.println($"  key #{Loop.count + 1}: {key}");
            }

        console.println("\nValues from a range:");
        for (Int n : 1..5)
            {
            console.println($"  {n}");
            }
        }
    }

Output:

Array of values:
  value #1: 10
  value #2: 20
  value #3: 30
  value #4: 40

Keys and values:
  x=42
  y=69

Just the keys:
  key #1: x
  key #2: y

Values from a range:
  1
  2
  3
  4
  5

Efene[edit]

Any data structure can be printed as a whole, preformated:

io.format("~p~n", [Collection])

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.

lists.foreach(fn (X) { io.format("~p~n", [X]) }, Collection)

Eiffel[edit]

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.

            across my_list as ic loop print (ic.item) end

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[edit]

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:

            across my_list as ic all ic.item.count > 3 end

Whereas, the following is true if at least one item has a count greater than three:

            across my_list as ic some ic.item.count > 3 end

Ela[edit]

open monad io
 
each [] = do return ()
each (x::xs) = do
  putStrLn $ show x
  each xs

Elena[edit]

ELENA 5.0 :

import system'routines;
import extensions;
 
public program()
{
    var things := new string[]{"Apple", "Banana", "Coconut"};
 
    things.forEach:(thing)
    {
        console.printLine:thing
    }
}

Elixir[edit]

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

Emacs Lisp[edit]

For a list either dolist macro

(dolist (x '(1 2 3 4))
  (message "x=%d" x))

or mapc function

(mapc (lambda (x)
        (message "x=%d" x))
      '(1 2 3 4))
Library: cl-lib
(cl-loop for x in '(1 2 3 4) do (message "x=%d" x))

Erlang[edit]

Any data structure can be printed as a whole, preformated:

io:format("~p~n",[Collection]).

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.

lists:foreach(fun(X) -> io:format("~p~n",[X]) end, Collection).

ERRE[edit]

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

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

Euphoria[edit]

Works with: OpenEuphoria
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
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

F#[edit]

We can use for directly or list iteration.

for i in [1 .. 10] do printfn "%d" i

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

Factor[edit]

{ 1 2 4 } [ . ] each

Fantom[edit]

Use each method to iterate over a collection of items in a List.

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

Fennel[edit]

sequential table[edit]

(each [k v (ipairs [:apple :banana :orange])]
  (print k v))
Output:
1       apple
2       banana
3       orange

key-value table[edit]

(each [k v (pairs {:apple :x :banana 4 :orange 3})]
  (print k v))
Output:
apple   x
banana  4
orange  3

Forth[edit]

create a 3 , 2 , 1 ,
: .array ( a len -- )
  cells bounds do  i @ .  cell +loop ;     \ 3 2 1

FOREACH[edit]

The thing about extensible languages is if you need FOREACH, you can have FOREACH. The Forth ' operator returns the "execution token" (XT) of a Forth word. An XT can be run with EXECUTE. If we apply an appropriate XT to all the elements of an array we have it.

: FOREACH  ( array size XT --)
        >R                 \ save execution token on return stack
        CELLS BOUNDS       \ convert addr,len -> last,first addresses
        BEGIN
           2DUP >          \ test addresses
        WHILE ( last>first )
           DUP R@ EXECUTE  \ apply the execution token to the address
           CELL+           \ move first to the next memory cell
        REPEAT
        R> DROP            \ clean return stack
        2DROP              \ and data stack
;

\ Make an operator to fetch contents of an address and print
: ?  ( addr --)  @ .  ;  

CREATE A[]   9 , 8 , 7 , 6 , 5 , 4 , 3 , 2 , 1 , 0 ,

\ Usage example:
A[] 10   ' ? FOREACH

Fortran[edit]

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

friendly interactive shell[edit]

Unlike, bash or csh, the PATH variable is automatically converted to real array.

for path in $PATH
    echo You have $path in PATH.
end

Sample output:

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

Frink[edit]

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.

array = [1, 2, 3, 5, 7]
for n = array
   println[n]

FutureBasic[edit]

window 1

void local fn DoIt
  CFArrayRef  array = @[@"Alpha",@"Bravo",@"Charlie",@"Delta",@"Echo",@"FutureBasic"]
  CFStringRef string
  
  for string in array
    print string
  next
end fn

fn DoIt

HandleEvents
Output:
Alpha
Bravo
Charlie
Delta
Echo
FutureBasic

GAP[edit]

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)

Go[edit]

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.

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

Groovy[edit]

"for" loop:

def beatles = ["John", "Paul", "George", "Ringo"]

for(name in beatles) {
    println name
}

"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.

beatles.each {
    println it
}

Output (same for either):

John
Paul
George
Ringo

Halon[edit]

$things = ["Apple", "Banana", "Coconut"];

foreach ($things as $thing) {
    echo $thing;
}

Haskell[edit]

import Control.Monad (forM_)
forM_ collect print

which is the same as

mapM_ print collect

Haxe[edit]

var a = [1, 2, 3, 4];

for (i in a)
  Sys.println(i);

HicEst[edit]

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

Hy[edit]

(for [x collection] (print x))

Icon and Unicon[edit]

The example below X can be a list, string, table or other data type.

procedure main()
X := [1,2,3,-5,6,9]
every x := !L do   
   write(x)
end

This loop can be written somewhat more concisely as:

every write(!L)

Io[edit]

collection foreach(println)

J[edit]

smoutput each i.10

Java[edit]

Works with: Java version 1.5+
Iterable<Type> collect;
...
for(Type i:collect){
   System.out.println(i);
}

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+
Iterable collect;
...
collect.forEach(o -> System.out.println(o));

This works with any Iterable, but not with arrays.

JavaScript[edit]

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

"alpha beta gamma delta".split(" ").forEach(function (x) {
    console.log(x);
});

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

console.log("alpha beta gamma delta".split(" ").map(function (x) {
    return x.toUpperCase(x);
}).join("\n"));

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

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

More generally, the following works for any object, including an array. It iterates over the keys of an object.

for (var a in o) {
    print(o[a]);
}

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:

for (var a in o) {
    if (o.hasOwnProperty(a)) {
        print(o[a]);
    }
}
Works with: JavaScript version 1.6
Deprecated

There is also a for each in construct that iterates over the values of an object:

h = {"one":1, "two":2, "three":3}
for (x in h) print(x);
for each (y in h) print(y);
Works with: ECMAScript version 6th edition

There is also a for of construct that iterates over the values of an object:

h = {"one":1, "two":2, "three":3}
for (x in h) print(x);
for (y of h) print(y);

jq[edit]

Iterables:

In this section, the array defined by "example" is used as an example:

def example: [1,2];

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:

example | .[]
# or equivalently: example[]
{"a":1, "b":2} | .[]
# or equivalently: {"a":1, "b":2}[]

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:

example | . as $a | range(0; length) | $a[.]

For JSON objects, the corresponding technique involves using keys, e.g.

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

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:

"abc" | . as $s | range(0;length) | $s[.:.+1]

"abc" | explode | map( [.]|implode) | .[]

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

Jsish[edit]

Jsi supports for of for looping over element of an array.

for (str of "alpha beta gamma delta".split(' ')) { puts(str); }
Output:
alpha
beta
gamma
delta

Julia[edit]

Translation of: Python
for i in collection
   println(i)
end

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.

K[edit]

   {`0:$x} ' !10
   _sin ' (1; 2; 3;)

Klingphix[edit]

include ..\Utilitys.tlhy

( -2 "field" 3.14159 ( "this" "that" ) ) len [get ?] for

" " input
Output:
-2
field
3.14159
("this", "that")

Kotlin[edit]

// 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()
}
Output:
alpha beta gamma delta
alpha beta gamma delta

LabVIEW[edit]

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.
LabVIEW Loops Foreach.png

Lambdatalk[edit]

{def collection alpha beta gamma delta} 
-> collection

{S.map {lambda {:i} {br}:i} {collection}} 
->
alpha 
beta 
gamma 
delta

or

{def S.foreach
 {lambda {:s}
  {if {S.empty? {S.rest :s}}
   then {S.first :s}
   else {S.first :s} {br}{S.foreach {S.rest :s}}}}}

{S.foreach {collection}}
->
alpha 
beta 
gamma 
delta

Lang5[edit]

: >>say.(*) . ;
5 iota >>say.

langur[edit]

A for in loop iterates over values and a for of loop iterates over indices.

for .i in [1, 2, 3] {
    writeln .i
}

val .abc = "abc"

for .i in .abc {
    writeln .i
}

for .i of .abc {
    writeln .abc[.i]
}

for .i in .abc {
    writeln cp2s .i
}
Output:
1
2
3
97
98
99
97
98
99
a
b
c

Lasso[edit]

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

LFE[edit]

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

LIL[edit]

# 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: $newlist"
Output:
prompt$ 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[edit]

days = ["monday", "tuesday", "wednesday", "thursday", "friday", "saturday", "sunday"]
repeat with day in days
  put day
end repeat

A callback-based forEach() can be implemented like this:

----------------------------------------
-- 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
days = ["monday", "tuesday", "wednesday", "thursday", "friday", "saturday", "sunday"]
forEach(days, #alert, _player)

Lisaac[edit]

"Lisaac loop foreach".split.foreach { word : STRING;
  word.print;
  '\n'.print;
};

LiveCode[edit]

Livecode's for each operates on chunks which may be words, items, lines, tokens. Example is for items.
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

[edit]

foreach [red green blue] [print ?]

Lua[edit]

Lua has 2 built-in iterators over tables.

pairs() iterates over all entries in a table, but in no particular order:

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

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.

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

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[edit]

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.

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

Maple[edit]

for p in [2, 3, 5, 7] do
    print(p);
end do;

Mathematica/Wolfram Language[edit]

Foreach over list of strings

s = (StringSplit@Import["ExampleData/USConstitution.txt"])[[1;;7]]; 
Do[
 Print@i,
 {i, s}
]

Output:

We
the
People
of
the
United
States,

MATLAB / Octave[edit]

    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;
    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;

A vectorized version of the code is

  printf('%d\n',list1);  
  printf('%s\n',list2{:});

Maxima[edit]

for n in [2, 3, 5, 7] do print(n);

MAXScript[edit]

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

Metafont[edit]

If we have a list of arbitrary items, we can simply use for:

for x = "mary", "had", "a", "little", "lamb": message x; endfor
end

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

for x = for i = 1 upto 9: a[i], endfor, a[10]: show x; endfor
end

works more like a foreach; we could make a macro to hide the strangeness of such a code.

min[edit]

Works with: min version 0.19.3
(1 2 3) 'puts foreach

MiniScript[edit]

for i in collection
   print i
end

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[edit]

things = {"Apple", "Banana", "Coconut"};
 
for thing in (things)
    player:tell(thing);
endfor

Nanoquery[edit]

Like Python, Nanoquery supports for...in syntax for list types and strings.

for item in collection
    println item
end

Some examples:

for n in {1,3,5,7,9}
	print n + " "
end
println

for char in "test string"
	print char
end
println
Output:
1 3 5 7 9 
test string

Nemerle[edit]

This works on anything which implements the IEnumerable interface.

def things = ["Apple", "Banana", "Coconut"];

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

NetRexx[edit]

/* 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

NewLISP[edit]

(map println '(Apple Banana Coconut))

Nim[edit]

let list = ["lorem", "ipsum", "dolor"]
for item in list:
  echo item
Output:
lorem
ipsum
dolor

Objeck[edit]

fruits := ["Apple", "Banana", "Coconut"];
each(i : fruits) {
  fruits[i]->PrintLine();
};

Objective-C[edit]

Works with: Objective-C version 2.0+
Works with: GNUstep
Works with: Cocoa
NSArray *collect;
//...
for(Type i in collect){
   NSLog(@"%@", i);
}

collect can be any object that adopts the NSFastEnumeration protocol.

Or (always using OpenStep compatible frameworks):

Works with: Objective-C version <2.0
NSArray *collect;
//...
NSEnumerator *enm = [collect objectEnumerator];
id i;
while( (i = [enm nextObject]) ) {
  // do something with object i
}

OCaml[edit]

List of integers:

List.iter
  (fun i -> Printf.printf "%d\n" i)
  collect_list

Array of integers:

Array.iter
  (fun i -> Printf.printf "%d\n" i)
  collect_array

Octave[edit]

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

We can also iterate over structures:

x.a = [ 10, 11, 12 ];
x.b = { "Cell", "ul", "ar" };
for [ val, key ] = x
  disp(key);
  disp(val);
endfor

Oforth[edit]

: printMonths | m | Date.Months forEach: m [ m . ] ;

But, apply can be used instead of a loop :

#. Date.Months apply

Ol[edit]

(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))
Output:
1
3
4
2

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

ooRexx[edit]

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.

/* 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

Output:

Loops/Foreach
Sunday Monday Tuesday Wednesday Thursday Friday Saturday

Oz[edit]

declare
  MyList = [1 2 3 4]
in
  {ForAll MyList Show}

  %% or:
  for E in MyList do {Show E} end

PARI/GP[edit]

for(i=1,#v,print(v[i]))

or (PARI/GP >= 2.4)

apply(x->print(x),v)

Pascal[edit]

See Delphi

Perl[edit]

foreach my $i (@collection) {
   print "$i\n";
}

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:

print "$_\n"  foreach @collection

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

foreach $l ( "apples", "bananas", "cherries" ) {
  print "I like $l\n";
}

Phix[edit]

sequence s = {-2,"field",3.14159268979,{"this","that"}}
for i=1 to length(s) do
    ?s[i]
end for

PHL[edit]

var numbers = 1..10;

numbers each # (number) [
    printf("%i\n", number);
];

PHP[edit]

foreach ($collect as $i) {
   echo "$i\n";
}

foreach ($collect as $key => $i) {
   echo "\$collect[$key] = $i\n";
}

foreach can also iterate over objects. By default it iterates over all visible fields of an object.

PicoLisp[edit]

(mapc println '(Apple Banana Coconut))

Pike[edit]

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

Iterating over the keys and values of a mapping (dictionary):

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

PL/I[edit]

declare A(10) fixed binary;
do i = lbound(A,1) to hbound(A,1);
   put skip list (A(i));
end;

Plain English[edit]

To run:
Start up.
Create a list.
Write each entry in the list to the console.
Destroy the list.
Wait for the escape key.
Shut down.

An entry is a thing with a number.

A list is some entries.

To add a number to a list:
Allocate memory for an entry.
Put the number into the entry's number.
Append the entry to the list.

To create a list:
Add 1 to the list.
Add 2 to the list.
Add 3 to the list.
Add 6 to the list.
Add 7 to the list.
Add 9 to the list.

To write an entry to the console:
Convert the entry's number to a string.
Write the string to the console.

To write each entry in a list to the console:
Get an entry from the list.
Loop.
If the entry is nil, exit.
Write the entry to the console.
Put the entry's next into the entry.
Repeat.
Output:
1
2
3
6
7
9

Pop11[edit]

Iteration over list:

lvars el, lst = [1 2 3 4 foo bar];
for el in lst do
   printf(el,'%p\n');
endfor;

PostScript[edit]

The forall operator performs a loop over a collection (array, string or dictionary). Strings and arrays can be treated very much the same:

[1 5 3 2] { = } forall
(abc) { = } forall

but dictionaries take a little more work since a key/value pair is pushed on the stack in each iteration:

<</a 25 /b 42>> {
  exch (Key: ) print
  =
  (Value: ) print
  =
} forall

PowerShell[edit]

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

Prolog[edit]

For example :

?- foreach(member(X, [red,green,blue,black,white]), writeln(X)).
red
green
blue
black
white
true.

Python[edit]

for i in collection:
   print i

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:

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

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:

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]))
Works with: Python version 2.x
d = {"fortytwo": 42, 3.14159: "pi", 23: "twentythree", "zero": 0, 13: "thirteen"}
for k in sorted(d):
    print("%s: %s" % (k, d[k]))

Quackery[edit]

$ "Sweet Boom Pungent Prickle Orange" nest$
witheach [ i times sp echo$ cr ]
Output:
    Sweet
   Boom
  Pungent
 Prickle
Orange

R[edit]

a <- list("First", "Second", "Third", 5, 6)
for(i in a) print(i)

Racket[edit]

#lang racket

;; an example sequence
(define sequence '("something" 1 2 "foo"))

;; works for any sequence
(for ([i sequence])
  (displayln i))

Raku[edit]

(formerly Perl 6)

Works with: Rakudo version 2015.10-40
say $_ for @collection;

Raku 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 ->.

for @collection -> $currentElement { say $currentElement; }

Raku will do it's best to put the topic at the right spot.

.say for @collection;
for @collection { .say };

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.

@collection>>.say;
@collection>>.=&infix:<+>(2); # increment each element by 2

REBOL[edit]

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 ""

Output:

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

Red[edit]

>> 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

ReScript[edit]

let fruits = ["apple", "banana", "coconut"]

Js.Array2.forEach(fruits, f => Js.log(f))

Retro[edit]

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

# 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
~~~

REXX[edit]

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.*/

Ring[edit]

aList = "Welcome to the Ring Programming Language"
for n in aList
    see n + nl
next

Ruby[edit]

for i in collection do
  puts i
end

This is syntactic sugar for:

collection.each do |i|
  puts i
end

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

Rust[edit]

Rust's for-loop already is a foreach-loop.

let collection = vec![1,2,3,4,5];
for elem in collection {
    println!("{}", elem);
}

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.

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);
}

Since Rust 1.21 foreach can be used explicitly executing a closure on each element.

let collection = vec![1, 2, 3, 4, 5];
collection.iter().for_each(|elem| println!("{}", elem));

Salmon[edit]

iterate (x; ["Red", "Green", "Blue"])
    x!;

output:

Red
Green
Blue

SAS[edit]

/* 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;

Sather[edit]

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;

Scala[edit]

val collection = Array(1, 2, 3, 4)
collection.foreach(println)

Alternatively:

(element <- 1 to 4).foreach(println)

Scheme[edit]

List:

(for-each
  (lambda (i) (display i) (newline))
  the_list)

Scilab[edit]

Works with: Scilab version 5.5.1
for e=["a","b","c"]
    printf("%s\n",e)
end
Output:
a
b
c

Seed7[edit]

The for loop of Seed7 can be used to loop over the elements of a container.

$ 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;

Self[edit]

aCollection do: [| :element | element printLine ].

(Provided that the objects in the collection understand the printLine method).

SETL[edit]

S := {1,2,3,5,8,13,21,34,55,89};
for e in S loop
    print(e);
end loop;

Sidef[edit]

foreach loop:

foreach [1,2,3] { |i|
    say i
}

for-in loop:

for i in [1,2,3] {
    say i
}

.each method:

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

Slate[edit]

c do: [| :obj | print: obj].

Smalltalk[edit]

aCollection do: [ :element | element displayNl ].

Provided that the objects in the collection understand the displayNl method (which can be added, if missing).

Most modern Smalltalks allow for a selector symbol to be sent a value: message; which allows for the very compact:

aCollection do:#displayNl.

(and because Aikido mentions it: of course this works for any kind of collection (and even things which simply implement a do: method to iterate on something)

(1 to:6 by:2) do:#displayNl.
'hello' do:#displayNl.
(Integer primesUpTo:100) do:#displayNl.
'/' asFilename directoryContents do:#displayNl.
((Smalltalk allClasses collect:#name) asSortedCollection to:2) do:#displayNl.

funnyClassLessObject := Plug new 
                          respondTo:#do: 
                          with:[:arg | 
                             arg value:'look ma'. 
                             arg value:'no classes needed'].
funnyClassLessObject do:#displayNl.
etc.
Output:

1 3 5 h e l l o 2 3 5 ... 97 home usr ... tmp cores AAAARecord AATree look ma no classes needed

Snabel[edit]

Prints foo, bar & baz followed by newlines.

['foo' 'bar' 'baz'] &say for

Sparkling[edit]

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

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

Standard ML[edit]

List of integers:

app
  (fn i => print (Int.toString i ^ "\n"))
  collect_list

Array of integers:

Array.app
  (fn i => print (Int.toString i ^ "\n"))
  collect_array

Stata[edit]

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

Suneido[edit]

for i in #(1, 2, 3)
    Print(i)

Swift[edit]

for i in [1,2,3] {
   print(i)
}

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

Alternately:

Works with: Swift version 2.x+
[1,2,3].forEach {
   print($0)
}

SystemVerilog[edit]

program main;
  int values[$];

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

Tailspin[edit]

Stream them

['a', 'b', 'c'] ... -> !OUT::write
Output:
abc

Lists/arrays can be put through an array transform to get the index as well

['a', 'b', 'c'] -> \[i]('$i;:$;
' -> !OUT::write \) -> !VOID
Output:
1:a
2:b
3:c

Tcl[edit]

foreach i {foo bar baz} {
    puts "$i"
}

Note that foreach also accepts multiple variables:

foreach {x y} {1 2 3 4} {
    puts "$x,$y"
}

And also multiple lists:

foreach i {1 2 3} j {a b c} {
    puts "$i,$j"
}

Or any combination of variables/list:

foreach i {1 2 3} {x y} {a b c d e f} {
    puts "$i,$x,$y"
}

Trith[edit]

[1 2 3 4 5] [print] each

TUSCRIPT[edit]

$$ MODE TUSCRIPT
week="Monday'Tuesday'Wednesday'Thursday'Friday'Saterday'Sunday"
LOOP day=week
PRINT day
ENDLOOP

Output:

Monday
Tuesday
Wednesday
Thursday
Friday
Saterday
Sunday

UNIX Shell[edit]

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

Works with: Bourne Shell
for file in *.sh; do
  echo "filename is $file"
done

If the list is in a shell parameter (like PATH), you adjust IFS.

Works with: Bourne Shell
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

Some shells have real arrays. The for loop can also iterate these.

Works with: Bash
collection=("first" "second" "third" "fourth" "something else")
for x in "${collection[@]}"; do
  echo "$x"
done
Works with: pdksh version 5.2.14
set -A collection "first" "second" "third" "fourth" "something else"
for x in "${collection[@]}"; do
  echo "$x"
done

C Shell[edit]

set collection=(first second third fourth "something else")
foreach x ($collection:q)
	echo $x:q
end

V[edit]

[1 2 3] [puts] step

Vala[edit]

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);
}

Vim Script[edit]

Vim Script's for-loop is actually a foreach-loop and iterates through a list.

for i in ["alpha", "beta", 42, 5.54]
    echo i
endfor

V (Vlang)[edit]

Translation of: go
fn print_all(values []int) {
   for i, x in values {
      println("Item $i = $x")
   }
}

Wart[edit]

each x '(1 2 3)
  prn x

WDTE[edit]

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

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

Wren[edit]

for (f in ["apples", "oranges", "pears"]) System.print(f)
Output:
apples
oranges
pears

XLISP[edit]

XLISP's FOR-EACH applies a procedure to each member of a list in turn.

(FOR-EACH PRINT '(CYRUS CAMBYSES DARIUS XERXES ARTAXERXES))
Output:
CYRUS 
CAMBYSES 
DARIUS 
XERXES 
ARTAXERXES

XPL0[edit]

Translation of C example:

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)];
]

XSLT[edit]

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.

<fo:block font-weight="bold">Adults:</fo:block>
<xsl:for-each select="person[@age &gt;= 21]">
  <fo:block><xsl:value-of select="position()"/>. <xsl:value-of select="@name"/></fo:block>
</xsl:for-each>

zig[edit]

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});
    }
}

zkl[edit]

Translation of: XPL0
foreach c in (T("Red","Green","Blue","Black","White"))
  { print(c," "); }
Output:
Red Green Blue Black White

Other forms of foreach, one that breaks apart a container into elements and one line nested loops.

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) }
Output:
123
456
146
156
246
256
346
356

Zig[edit]

const std = @import("std");

pub fn main() !void {
    const stdout_wr = std.io.getStdOut().writer();

    // 1. Index element index sizes are comptime-known
    const a1: []const u8 = &[_]u8{ 'a', 'b', 'c' };
    // also works with slices
    //const a2: [] u8 = &a1;
    for (a1) |el_a|
        try stdout_wr.print("{c}\n", .{el_a});
    // 2. Index element index sizes are not comptime-known
    // Convention is to provide a `next()` method.
    // TODO
}