Loops/Foreach: Difference between revisions

{{trans|C#}}

L(thing) things

=={{header|ACL2}}==

(if (endp xs)

nil

(prog2$ (cw "~x0~%" (first xs))

<pre>

=={{header|Action!}}==

In Action! there is no for-each loop.

DEFINE PTR="CARD"

BYTE i

PrintE(items(i))

OD

{{out}}

[https://gitlab.com/amarok8bit/action-rosetta-code/-/raw/master/images/Foreach.png Screenshot from Atari 8-bit computer]

=={{header|Ada}}==

===arrays===

use Ada.Integer_Text_IO;

end loop;

Alternative solution (Ada 2012):

Put( Item );

===doubly linked lists===

{{works with|Ada 2005}}

use Ada.Integer_Text_IO, Ada.Containers;

DL_List.Iterate (Print_Node'Access);

===vectors===

{{works with|Ada 2005}}

use Ada.Integer_Text_IO, Ada.Containers;

V.Iterate (Print_Element'Access);

=={{header|Aikido}}==

Aikido's <code>foreach</code> loop allows iteration through multiple value types.

===strings===

foreach ch str { // you can also use an optional 'in'

println (ch) // one character at a time

===vectors===

foreach v vec { // you can also use an optional 'in'

println (v)

===maps===

foreach city cities {

println (city.first + " has population " + city.second)

===integers===

println (i) // prints values 0..99

}

foreach i a..b {

println (i) // prints values from a to b (20..10)

===Objects===

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

class Element (public data) {

public var next = null

foreach n list {

println (n)

===Coroutines===

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

function squares (start, end) {

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

foreach s squares (start, end) {

println (s)

===Files===

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

foreach line s {

print (line)

===Enumerations===

RED, GREEN, BLUE

}

foreach color Color {

println (color)

=={{header|Aime}}==

integer i, v;

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

=={{header|ALGOL 68}}==

{{works with|ALGOL 68G|Any - tested with release mk15-0.8b.fc9.i386}}

{{works with|ELLA ALGOL 68|Any (with appropriate job cards) - tested with release 1.8.8d.fc9.i386}}

FOR index FROM LWB collection TO UPB collection DO

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

Output:

<pre>

<br>

<br>[[ALGOL 68RS]] and [[Algol68toc]] have a FORALL loop, the following is equivalent to the example above:

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

=={{header|AmigaE}}==

DEF a_list : PTR TO LONG, a

a_list := [10, 12, 14]

-> if the "action" fits a single statement, we can do instead

ForAll({a}, a_list, `WriteF('\d\n', a))

=={{header|Apex}}==

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

System.debug(i);

}

=={{header|AppleScript}}==

log contents of fruit

=={{header|Arturo}}==

dict: #[

loop dict [key val]->

{{out}}

<pre>one

=={{header|AutoHotkey}}==

Loop, Parse, string, `,

=={{header|AWK}}==

The <code>for (element_index in array)</code> 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, " ")

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,

So to iterate over the array's elements in the ''right'' order,

a normal loop can be used:

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:

BEGIN {

for (el in "apples","bananas","cherries") {

print "I like " el

}

=={{header|BASIC}}==

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

FOR x$ IN "Hello cruel world"

PRINT x$

FOR y$ IN "1,2,\"3,4\",5" STEP ","

PRINT y$

{{out}}

==={{header|BASIC256}}===

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

collection$ = { "The", "quick", "brown", "fox", "jumps", "over", "the", "lazy", "dog." }

PRINT collection$[i]+ " ";

NEXT i

Output:

<pre>The quick brown fox jumps over the lazy dog.</pre>

==={{header|BBC BASIC}}===

{{works with|BBC BASIC for Windows}}

collection$() = "The", "quick", "brown", "fox", "jumps", \

\ "over", "the", "lazy", "dog."

PRINT collection$(index%) " ";

NEXT

==={{header|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

20 REM *** FILL ARRAY WITH WORDS ***

30 FOR I = 0 TO 8

90 NEXT

100 END

==={{header|Creative Basic}}===

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

'because this is a console only program.

END

==={{header|FreeBASIC}}===

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

Print

{{out}}

==={{header|Gambas}}===

'''[https://gambas-playground.proko.eu/?gist=cb94500c68749f6f93915f3f10de5a03 Click this link to run this code]'''

Dim siInput As Short[] = [1, 8, 0, 6, 4, 7, 3, 2, 5, 9]

Dim siTemp As Short

Next

{{out}}

<pre>

==={{header|IS-BASIC}}===

110 LET I=1

120 DO

170 PRINT COLLECTION$(J);" ";

180 NEXT

==={{header|IWBASIC}}===

'''Linked List'''

AList=ListCreate()

'Because this is a console only program.

'''An Array'''

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

'Because this is a console only program.

END

==={{header|Lambdatalk}}===

{def collection alpha beta gamma delta}

-> collection

delta

==={{header|Liberty BASIC}}===

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

element$ =""

i =1 ' used to point to successive elements

loop until 1 =2

Not good!

Hardly good!

==={{header|NS-HUBASIC}}===

20 REM ADD DATA TO ARRAY AND PRINT ARRAY CONTENTS

30 FOR I=0 TO 8

50 PRINT A$(I)" ";

60 NEXT

==={{header|PureBasic}}===

Works for LinkedLists and Maps

PrintN(element())

==={{header|Run BASIC}}===

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

i = i + 1

print word$(t$,i,",")

==={{header|TI-89 BASIC}}===

Define strs = {"Lorem","ipsum","dolor"}

For i, 1, dim(strs)

Disp strs[i]

==={{header|VBA}}===

Dim FruitArray() As Variant

Dim Fruit As Variant

Debug.Print Fruit

Next Fruit

==={{header|VBScript}}===

For Each x In items

WScript.Echo x

==={{header|Visual Basic .NET}}===

list.Add("Car")

list.Add("Boat")

For Each item In list

Console.WriteLine(item)

==={{header|Yabasic}}===

//Mediante un bucle FOR iteramos a través de una matriz por índice.

//READ-DATA se usa para rellenar la matriz

next each

print

'''Direct usage:'''

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

echo %%A

'''Using a Collection Variable:'''

set "collection=This is a sample collection"

for %%A in (%collection%) do (

echo %%A

{{Out|They have the Same Output}}

<pre>This

=={{header|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.

a[1] = 234

a[3] = 95.6

for (i = 0; i < 4; i++) {

a[i]

=={{header|Bracmat}}==

Bracmat has a more or less traditional 'while' loop (<code>whl'<i>expression</i></code>) 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:

= Afrikaans

Ελληνικά

മലയാളം

ئۇيغۇرچە

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

The tail-recursive solution. When the auxiliary variable is reduced to nothing, the loop fails. By adding the <code>~</code> flag to the initial invocation, failure is turned into success. This solution benefits from tail recursion optimization.

& ( loop

= !L:%?language ?L

& !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 <code>@</code> flag matches at most one element. The <code>%</code> flag matches at least one element. Together they ensure that exactly one language name is assigned to the variable <code>language</code>. After all elements have been done, control is passed to the rhs of the <code>|</code> operator.

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

|

=={{header|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.

...

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.<BR><BR>

C string as a collection of char

#include <stdio.h>

#include <stdlib.h>

return(0);

}

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

#include <stdio.h>

#include <stdlib.h>

return(0);

}

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

: ''Note: idxtype can be removed and [http://gcc.gnu.org/onlinedocs/gcc/Typeof.html typeof(col&#91;0&#93;)] can be used in it's place with [[GCC]]''

#include <stdio.h>

#include <stdlib.h>

return(0);

}

=={{header|C sharp|C#}}==

foreach (string thing in things)

{

Console.WriteLine(thing);

=={{header|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 <tt>container_type</tt> and the actual container object is named container.

{

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

However the idiomatic way to output a container would be

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

{

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

...

{{works with|C++11}}

{

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

Here <tt>container</tt> is the container variable, <tt>element</tt> 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:

{

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):

{

element += 42;

=={{header|Chapel}}==

=={{header|Clojure}}==

=={{header|CLU}}==

one needs to explicitly use the <code>elements</code> iterator.

po: stream := stream$primary_output()

stream$putl(po, word)

end

=={{header|CMake}}==

foreach(file ${list})

message(${file})

=={{header|COBOL}}==

{{trans|C#}}

{{works with|Visual COBOL}}

...

set content of things to ("Apple", "Banana", "Coconut")

perform varying thing as string through things

display thing

=={{header|ColdFusion}}==

<Cfloop list="Fee, Fi, Foe, Fum" index="i">

<Cfoutput>#i#!</Cfoutput>

</Cfloop>

=={{header|Common Lisp}}==

or

or

or

(iter

(for x in the-list)

=== Using DO ===

(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

{{out}}

=={{header|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.

void main() {

foreach (key, value; collection3)

writeln(key, " ", value);

{{out}}

<pre>A

=={{header|Dao}}==

=={{header|Delphi}}==

Supports arrays (single, multidimensional, and dynamic), sets, strings, collections and any class or interface that implements GetEnumerator().

{$APPTYPE CONSOLE}

for s in 'Hello' do

Writeln(s);

Output:

<pre>H

=={{header|Dragon}}==

for value : array {

showln value

}

=={{header|Dyalect}}==

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:

print(i)

This would perfectly work with any custom iterator as well:

yield 1

yield 2

for i in myCollection() {

print(i)

All three code samples would output:

=={{header|E}}==

println(e)

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

=={{header|EchoLisp}}==

(define my-list '( albert simon antoinette))

(for ((h my-list)) (write h))

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

=={{header|Efene}}==

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

However, to iterate over each element of a list, Efene uses <tt>lists.map/2</tt>, except in the case of IO where <tt>lists.foreach/2</tt> has to be used as the evaluation order is defined to be the same as the order of the elements in the list.

=={{header|Eiffel}}==

{{works with|EiffelStudio|6.6 beta (with provisional loop syntax)}}

The iteration (foreach) form of the Eiffel loop construct is introduced by the keyword <code lang="eiffel">across</code>.

The local entity <code lang="eiffel">ic</code> is an instance of the library class <code lang="eiffel">ITERATION_CURSOR</code>. The cursor's feature <code lang="eiffel">item</code> provides access to each structure element. Descendants of class <code lang="eiffel">ITERATION_CURSOR</code> can be created to handle specialized iteration algorithms. The types of objects that can be iterated across (<code lang="eiffel">my_list</code> in the example) are based on classes that inherit from the library class <code lang="eiffel">ITERABLE</code>

===Boolean expression variant===

This iteration is a boolean expression which is true if all items in <code>my_list</code> have counts greater than three:

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

=={{header|Ela}}==

each [] = do return ()

each (x::xs) = do

putStrLn $ show x

=={{header|Elena}}==

ELENA 5.0 :

import extensions;

console.printLine:thing

}

=={{header|Elixir}}==

[1, 3.14, "abc", [3], {0, 5}]

iex(2)> Enum.each(list, fn x -> IO.inspect x end)

[3]

{0, 5}

=={{header|Emacs Lisp}}==

For a list either <code>dolist</code> macro

or <code>mapc</code> function

(message "x=%d" x))

{{libheader|cl-lib}}

=={{header|Erlang}}==

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

However, to iterate over each element of a list, Erlang uses <tt>lists:map/2</tt>, except in the case of IO where <tt>lists:foreach/2</tt> has to be used as the evaluation order is defined to be the same as the order of the elements in the list.

=={{header|ERRE}}==

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

=={{header|Euphoria}}==

{{works with|OpenEuphoria}}

include std/console.e

if getc(0) then end if

{{out}}

<pre>

=={{header|F_Sharp|F#}}==

We can use ''for'' directly or list iteration.

=={{header|Factor}}==

=={{header|Fantom}}==

Use <code>each</code> method to iterate over a collection of items in a <code>List</code>.

{

public static Void main ()

}

}

=={{header|Fennel}}==

====sequential table====

{{out}}

<pre>1 apple

3 orange</pre>

====key-value table====

{{out}}

<pre>apple x

orange 3</pre>

=={{header|Forth}}==

: .array ( a len -- )

===FOREACH===

The thing about extensible languages is if you need FOREACH, you can have FOREACH.

If we apply an appropriate XT to all the elements of an array we have it.

>R \ save execution token on return stack

CELLS BOUNDS \ convert addr,len -> last,first addresses

\ Usage example:

=={{header|Fortran}}==

implicit none

write(*,'(A)') colors

=={{header|friendly interactive shell}}==

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

echo You have $path in PATH.

Sample output:

=={{header|Frink}}==

Frink's <CODE>for</CODE> 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]

=={{header|GAP}}==

Print(p, "\n");

od;

(1,3,4)

(1,2)(3,4)

=={{header|Go}}==

<code>range</code> 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.

for i, x := range values {

fmt.Printf("Item %d = %d\n", i, x)

}

=={{header|Groovy}}==

"for" loop:

for(name in beatles) {

println name

"each()" method:<br>

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.

println it

Output (same for either):

<pre>John

=={{header|Halon}}==

foreach ($things as $thing) {

echo $thing;

=={{header|Haskell}}==

which is the same as

=={{header|Haxe}}==

for (i in a)

=={{header|HicEst}}==

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

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

WRITE() today

=={{header|Hy}}==

=={{header|Icon}} and {{header|Unicon}}==

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

X := [1,2,3,-5,6,9]

every x := !L do

write(x)

This loop can be written somewhat more concisely as:

=={{header|Io}}==

=={{header|J}}==

=={{header|Java}}==

{{works with|Java|1.5+}}

...

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|1.8+}}

Iterable collect;

...

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

This works with any Iterable, but not with arrays.

=={{header|JavaScript}}==

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

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()''',

return x.toUpperCase(x);

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

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.

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:

if (o.hasOwnProperty(a)) {

print(o[a]);

}

{{works with|JavaScript|1.6}}

;Deprecated

There is also a <tt>[https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Statements/for_each...in for each in]</tt> construct that iterates over the values of an object:

for (x in h) print(x);

{{works with|ECMAScript|6th edition}}

There is also a <tt>[https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Statements/for...of for of]</tt> construct that iterates over the values of an object:

for (x in h) print(x);

=={{header|jq}}==

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

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:

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:

For JSON objects, the corresponding technique involves using <tt>keys</tt>, e.g.

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

produces:

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

To convert the constituent characters (or technically, codepoints) of a string into a stream of values, there are two techniques illustrated by these examples:

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

=={{header|Jsish}}==

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

{{out}}

=={{header|Julia}}==

{{trans|Python}}

println(i)

The Julia <code>for</code> statement is always a "foreach", and the built-in <code>start:end</code> or <code>start:step:end</code> "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.

=={{header|K}}==

=={{header|Klingphix}}==

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

{{out}}

<pre>-2

=={{header|Kotlin}}==

fun main(args: Array<String>) {

greek.forEach { print("$it ") }

println()