Loop over multiple arrays simultaneously

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Task
Loop over multiple arrays simultaneously
You are encouraged to solve this task according to the task description, using any language you may know.

Loop

over multiple arrays (or lists or tuples or whatever they're called in 

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

For this example, loop over the arrays (a,b,c),

(A,B,C) and (1,2,3) 

to produce the output

aA1
bB2
cC3

If possible, also describe what happens when the arrays are of different

lengths.

Contents

[edit] ACL2

(defun print-lists (xs ys zs)
(if (or (endp xs) (endp ys) (endp zs))
nil
(progn$ (cw (first xs))
(cw "~x0~x1~%"
(first ys)
(first zs))
(print-lists (rest xs)
(rest ys)
(rest zs)))))
 
(print-lists '("a" "b" "c") '(A B C) '(1 2 3))

[edit] Ada

with Ada.Text_IO;  use Ada.Text_IO;
 
procedure Array_Loop_Test is
type Array_Index is range 1..3;
A1 : array (Array_Index) of Character := "abc";
A2 : array (Array_Index) of Character := "ABC";
A3 : array (Array_Index) of Integer  := (1, 2, 3);
begin
for Index in Array_Index'Range loop
Put_Line (A1 (Index) & A2 (Index) & Integer'Image (A3
(Index))(2));
end loop;
end Array_Loop_Test;

[edit] ALGOL 68

Works with: ALGOL 68 version Revision 1 - no extensions to language used
[]UNION(CHAR,INT) x=("a","b","c"), y=("A","B","C"), 
z=(1,2,3);
FOR i TO UPB x DO
printf(($ggd$, x[i], y[i], z[i], $l$))
OD
Output:
aA1
bB2
cC3

[edit] AWK

BEGIN {
split("a,b,c", a, ",");
split("A,B,C", b, ",");
split("1,2,3", c, ",");
 
for(i = 1; i <= length(a); i++) {
print a[i] b[i] c[i];
}
}

[edit] AutoHotkey

[edit] Pseudo-arrays

StringSplit creates a pseudo-array

List1 = a,b,c
List2 = A,B,C
List3 = 1,2,3
MsgBox, % LoopMultiArrays()
 
List1 = a,b,c,d,e
List2 = A,B,C,D
List3 = 1,2,3
MsgBox, % LoopMultiArrays()
 
 
;---------------------------------------------------------------------------
LoopMultiArrays()
 
{ ; print the ith element of each
;---------------------------------------------------------------------------
 
 
local Result
StringSplit, List1_, List1, `,
StringSplit, List2_, List2, `,
StringSplit, List3_, List3, `,
Loop, % List1_0
Result .= List1_%A_Index% List2_%A_Index% List3_%A_Index% "`n"
Return, Result
}

An array that is too short on creation will return empty strings when trying to retrieve further elements. The 2nd Message box shows:

aA1
bB2
cC3
dD
e

[edit] Real arrays

Works with: AutoHotkey_L

In AutoHotkey_L, we can use true arrays (Objects) and the For loop.

List1 := ["a", "b", "c"]
List2 := ["A", "B", "C"]
List3 := [ 1 , 2 , 3 ]
MsgBox, % LoopMultiArrays()
 
List1 := ["a", "b", "c", "d", "e"]
List2 := ["A", "B", "C", "D"]
List3 := [1,2,3]
MsgBox, % LoopMultiArrays()
 
 
LoopMultiArrays() {
local Result
For key, value in List1
Result .= value . List2[key] . List3[key] "`n"
Return, Result
}

The output from this script is identical to the first one.

[edit] Axe

Note that in this example, we use a few bytes from each of L₁, L₂, and L₃ for simplicity. In practice, one would want to arrange the arrays to all fit within L₁ to avoid volatility issues with L₂ and L₃.

'a'→{L₁}
'b'→{L₁+1}
'c'→{L₁+2}
'A'→{L₂}
'B'→{L₂+1}
'C'→{L₂+2}
1→{L₃}
2→{L₃+1}
3→{L₃+2}
For(I,0,2)
Disp {L₁+I}►Char,{L₂+I}►Char,{L₃+I}►Dec,i
End

[edit] Babel

There are two ways to do this in Babel. First, you could transpose the lists:

main: { (('a' 'b' 'c')('A' 'B' 'C')('1' '2' '3')) 
simul_array }
 
simul_array!:
{ trans
{ { << } each "\n" << } each }

The 'trans' operator substitutes nil in the portions of each transposed column wherever a row list was shorter than the longest row list. The '<<' operator prints nothing if the top-of-stack is nil.

A more literal solution to the problem as presented would be to iterate across each list using a user-defined cdrall operator:

main: { (('a' 'b' 'c')('A' 'B' 'C')('1' '2' '3')) 
simul_array }
 
simul_array!:
{{ dup
{ car << } each
cdrall }
{ allnil? not }
while }
 
cdrall!: { { { cdr } each -1 take } nest }
 
-- only returns true if all elements of a list are nil
allnil?!:
{ 1 <->
{ car nil?
{ zap 0 last }
{ nil }
if} each }

This solution is formally identical to the first and will handle lists of varying lengths by printing inserting nil and printing nothing for the tail ends

of the 

short lists.

[edit] BBC BASIC

      DIM array1$(2), array2$(2), array3%(2)
array1$() = "a", "b", "c"
array2$() = "A", "B", "C"
array3%() = 1, 2, 3
 
FOR index% = 0 TO 2
PRINT array1$(index%) ; array2$(index%) ; array3%(index%)
NEXT

[edit] C

Given several arrays, especially if they are heterogeneous, the most ordinary way to loop over all of them is to simply use an index variable. Determining when to stop is generally done in some application-specific way.

#include <stdio.h>
 
char a1[] = {'a','b','c'};
char a2[] = {'A','B','C'};
int a3[] = {1,2,3};
 
int main(void) {
for (int i = 0; i < 3; i++) {
printf("%c%c%i\n", a1[i], a2[i], a3[i]);
}
}

(Note: Some compilers may require a flag to accept this modern C code, such as gcc -std=c99.)

On the other hand, it is possible to write a more generic higher-order iteration scheme, as demonstrated in this example.

There, a type for arrays with runtime-specified lengths and polymorphic
printing is defined, and the iteration continues up to the length of 

the shortest array.

[edit] C#

class Program
{
static void Main(string[] args)
{
char[] a = { 'a', 'b', 'c' };
char[] b = { 'A', 'B', 'C' };
int[] c = { 1, 2, 3 };
int min = Math.Min(a.Length, b.Length);
min = Math.Min(min, c.Length);
for (int i = 0; i < min; i++)
Console.WriteLine("{0}{1}{2}", a[i], b[i], c[i]);
}
}


Using Zip:

 
int[] numbers = { 1, 2, 3, 4 };
string[] words = { "one", "two", "three" };
Console.WriteLine(numbers.Zip(words, (first, second) => first + " " +
second));
 
 

Like a perl programmer would write it:

 
Console.WriteLine((new[] { 1, 2, 3, 4 }).Zip(new[] { "a", "b", "c" },
(f, s) => f + " " + s));
 

[edit] C++

With std::vectors:

#include <iostream>
#include <vector>
 
int main(int argc, char* argv[])
{
std::vector<char> ls(3); ls[0] = 'a'; ls[1] = 'b'; ls[2] = 'c';
std::vector<char> us(3); us[0] = 'A'; us[1] = 'B'; us[2] = 'C';
std::vector<int> ns(3); ns[0] = 1; ns[1] = 2; ns[2] = 3;
 
std::vector<char>::const_iterator lIt = ls.begin();
std::vector<char>::const_iterator uIt = us.begin();
std::vector<int>::const_iterator nIt = ns.begin();
for(; lIt != ls.end() && uIt != us.end() && nIt !=
ns.end();
++lIt, ++uIt, ++nIt)
{
std::cout << *lIt << *uIt << *nIt << "\n";
}
}

Using static arrays:

#include <iostream>
 
int main(int argc, char* argv[])
{
char ls[] = {'a', 'b', 'c'};
char us[] = {'A', 'B', 'C'};
int ns[] = {1, 2, 3};
 
for(size_t li = 0, ui = 0, ni = 0;
li < sizeof(ls) && ui < sizeof(us) && ni
< sizeof(ns) / sizeof(int);
++li, ++ui, ++ni)
{
std::cout << ls[li] << us[ui] << ns[ni] <<
"\n";
}
}

[edit] Clojure

(doseq [s (map #(str %1 %2 %3) "abc" "ABC" "123")] 
(println s))

The sequence stops when the shortest list is exhausted.

[edit] COBOL

       IDENTIFICATION DIVISION.
PROGRAM-ID. Loop-Over-Multiple-Tables.
 
DATA DIVISION.
WORKING-STORAGE SECTION.
01 A VALUE "abc".
03 A-Vals PIC X OCCURS 3 TIMES.
 
01 B VALUE "ABC".
03 B-Vals PIC X OCCURS 3 TIMES.
 
01 C VALUE "123".
03 C-Vals PIC 9 OCCURS 3 TIMES.
 
01 I PIC 9.
 
PROCEDURE DIVISION.
PERFORM VARYING I FROM 1 BY 1 UNTIL 3 < I
DISPLAY A-Vals (I) B-Vals (I) C-Vals (I)
END-PERFORM
 
GOBACK
.

[edit] Common Lisp

[edit] Using functional application

(mapc (lambda (&rest args)
(format t "~{~A~}~%" args))
'(|a| |b| |c|)
'(a b c)
'(1 2 3))

If lists are different lengths, it stops after the shortest one.

[edit] Using LOOP

 
(loop for x in '("a" "b" "c")
for y in '(a b c)
for z in '(1 2 3)
do (format t "~a~a~a~%" x y z))
 

[edit] Chapel

var a1 = [ "a", "b", "c" ];
var a2 = [ "A", "B", "C" ];
var a3 = [ 1, 2, 3 ];
 
for (x,y,z) in zip(a1, a2, a3) do
writeln(x,y,z);

[edit] D

import std.stdio, std.range;
 
void main () {
foreach (a, b, c; zip("abc", "ABC", [1, 2, 3]))
writeln(a, b, c);
}
Output:
aA1
bB2
cC3

zip() allows to specify the stopping policy. On default it stops when the shortest range is exhausted (same as StoppingPolicy.shortest):

import std.stdio, std.range;
 
void main () {
auto a1 = [1, 2];
auto a2 = [1, 2, 3];
alias StoppingPolicy sp;
 
// Stops when the shortest range is exhausted
foreach (p; zip(sp.shortest, a1, a2))
writeln(p.tupleof);
writeln();
 
// Stops when the longest range is exhausted
foreach (p; zip(sp.longest, a1, a2))
writeln(p.tupleof);
writeln();
 
// Requires that all ranges are equal
foreach (p; zip(sp.requireSameLength, a1, a2))
writeln(p.tupleof);
}
Output:
11
22

11
22
03

11
22

Followed by an exception with message "Inequal-length ranges passed to Zip".

There is also std.range.lockstep:

import std.stdio, std.range;
 
void main() {
auto arr1 = [1, 2, 3, 4, 5];
auto arr2 = [6, 7, 8, 9, 10];
 
foreach (ref a, ref b; lockstep(arr1, arr2))
a += b;
 
assert(arr1 == [7, 9, 11, 13, 15]);
 
// Lockstep also supports iteration with an index variable
foreach (index, a, b; lockstep(arr1, arr2))
writefln("Index %s: a = %s, b = %s", index, a, b);
}

Lower level code that stops at the shortest length:

import std.stdio, std.algorithm;
 
void main () {
auto s1 = "abc";
auto s2 = "ABC";
auto a1 = [1, 2];
 
foreach (i; 0 .. min(s1.length, s2.length, a1.length))
writeln(s1[i], s2[i], a1[i]);
}
Output:
aA1
bB2

[edit] Delphi

program LoopOverArrays;
 
{$APPTYPE CONSOLE}
 
uses SysUtils;
 
const
ARRAY1: array [1..3] of string = ('a', 'b', 'c');
ARRAY2: array [1..3] of string = ('A', 'B', 'C');
ARRAY3: array [1..3] of Integer = (1, 2, 3);
var
i: Integer;
begin
for i := 1 to 3 do
Writeln(Format('%s%s%d', [ARRAY1[i], ARRAY2[i], ARRAY3[i]]));
 
Readln;
end.

[edit] DWScript

If the arrays don't have the same bounds, an index out of bound exception will be triggered when attempting to access a non-existing element.

const a1 = ['a', 'b', 'c'];
const a2 = ['A', 'B', 'C'];
const a3 = [1, 2, 3];
 
var i : Integer;
for i := 0 to 2 do
PrintLn(Format('%s%s%d', [a1[i], a2[i], a3[i]]));

[edit] E

E lacks a nice way to do this; this is [http://wiki.erights.org/wiki/Parallel_iteration to be fixed, once we figure out what to do]. However, iteration over an List produces its indexes as keys, so a not entirely awful idiom exists:

def a1 := ["a","b","c"]
def a2 := ["A","B","C"]
def a3 := ["1","2","3"]
 
for i => v1 in a1 {
println(v1, a2[i], a3[i])
}

This will obviously fail if a2 or a3 are shorter than a1, and omit items

if a2 or a3 are longer.

Given a parallel iteration utility, we might write this:

for [v1, v2, v3] in zip(a1, a2, a3) {
println(v1, v2, v3)
}

zip cannot yet be defined for all collections (other than by iterating over each one and storing the results in a List

first); but we can define it for numeric-indexed collections such as 

Lists, as below. Both a definition for any number of collections and two

collections is given; the latter in order to demonstrate the principle 

without the clutter resulting from handling a variable number of collections.

def zip {
to run(l1, l2) {
def zipped {
to iterate(f) {
for i in int >= 0 {
f(i, [l1.fetch(i, fn { return }),
l2.fetch(i, fn { return })])
}
}
}
return zipped
}
 
match [`run`, lists] {
def zipped {
to iterate(f) {
for i in int >= 0 {
var tuple := []
for l in lists {
tuple with= l.fetch(i, fn { return })
}
f(i, tuple)
}
}
}
zipped
}
}

(This will stop when the end of the shortest collection is reached.)

[edit] Efene

@public 
run = fn () {
lists.foreach(fn ((A, B, C)) { io.format("~s~n", [[A, B, C]]) },
lists.zip3("abc", "ABC", "123"))
}
 

If the lists are not all the same length, an error is thrown.

[edit] Ela

open console list imperative
 
xs = zipWith3 (\x y z -> show x ++ show y ++ show z) ['a','b','c']
['A','B','C'] [1,2,3]
 
each writen xs

The code above can be written shorter. First there is no need in lists as soon as strings in Ela can be treated as lists. Also instead of explicit labmda one can use partial application and a standard composition operator:

xs = zipWith3 (\x -> (x++) >> (++)) "abc" "ABC"
"123"

[edit] Erlang

Shortest option:

lists:zipwith3(fun(A,B,C)-> 
io:format("~s~n",[[A,B,C]]) end, "abc", "ABC", "123").

However, as every expression in Erlang has to return something, printing

text returns 'ok'. A list with as many 'ok's as there are lines printed
will thus be created.

The technically cleanest way to do things would be with lists:foreach/2, which also guarantees evaluation order:

lists:foreach(fun({A,B,C}) ->  
io:format("~s~n",[[A,B,C]]) end,
lists:zip3("abc", "ABC", "123")).

If the lists are not all the same length, an error is thrown.

[edit] Euphoria

There are many ways to do this. All of them rely on what strings really

are.

If they are all "strings", it's quite easy:

 
sequence a, b, c
 
a = "abc"
b = "ABC"
c = "123"
 
for i = 1 to length(a) do
puts(1, a[i] & b[i] & c[i] & "\n")
end for
 

If not, and the other sequence is known to contain only integers:

 
sequence a, b, c
 
a = "abc"
b = "ABC"
c = {1, 2, 3}
 
for i = 1 to length(a) do
printf(1, "%s%s%g\n", {a[i], b[i], c[i]})
end for
 

A general solution for any arbitrary strings of characters or numbers can get a bit complex. This is because of how sequences are stored and printed out. One possible answer is as follows, if you know that only alphanumeric characters are used:

 
for i = 1 to length(a) do
if (a[i] >= '0' and a[i] <= '9') then
a[i] -= '0'
end if
if (b[i] >= '0' and b[i] <= '9') then
b[i] -= '0'
end if
if (c[i] >= '0' and c[i] <= '9') then
c[i] -= '0'
end if
printf(1, "%s%s%s\n", {a[i], b[i], c[i]})
end for
 

Just as in Java, using single quotes around a character gives you its "char value". In Euphoria, though, it is simply that character's code in ASCII.

With all three of the above solutions, if any of the strings are smaller

than the first, it will return an error.

[edit] Factor

"abc" "ABC" "123" [ [ write1 ] tri@ nl ] 
3each

[edit] Fantom

This will stop when it reaches the end of the shortest list.

 
class LoopMultiple
{
public static Void main ()
{
List arr1 := ["a", "b", "c"]
List arr2 := ["A", "B", "C"]
List arr3 := [1, 2, 3]
[arr1.size, arr2.size, arr3.size].min.times |Int i|
{
echo ("${arr1[i]}${arr2[i]}${arr3[i]}")
}
}
}
 

[edit] Forth

create a  char a , char b , char c ,
create b char A , char B , char C ,
create c char 1 , char 2 , char 3 ,
 
: main
3 0 do cr
a i cells + @ emit
b i cells + @ emit
c i cells + @ emit
loop
cr
a b c
3 0 do cr
3 0 do
rot dup @ emit cell+
loop
loop
drop drop drop
;

[edit] Fortran

program main
implicit none
 
integer,parameter :: n_vals = 3
character(len=*),dimension(n_vals),parameter :: ls = ['a','b','c']
character(len=*),dimension(n_vals),parameter :: us = ['A','B','C']
integer,dimension(n_vals),parameter :: ns = [1,2,3]
 
integer :: i !counter
 
do i=1,n_vals
write(*,'(A1,A1,I1)') ls(i),us(i),ns(i)
end do
 
end program main
 

[edit] F#

for c1,c2,n in Seq.zip3 ['a';'b';'c'] ['A';'B';'C'] 
[1;2;3] do
printfn "%c%c%d" c1 c2 n

When one sequence is exhausted, any remaining elements in the other sequences are ignored.

[edit] FunL

import lists.zip3
 
for x <- zip3( ['a', 'b', 'c'], ['A', 'B', 'C'], [1, 2, 3] )
println( x.mkString() )
Output:
aA1
bB2
cC3

[edit] GAP

 
# The Loop function will apply some function to every tuple built by
taking
# the i-th element of each list. If one of them is exhausted before the
others,
# the loop continues at its begining. Only the longests lists will be
precessed only once.
Loop := function(a, f)
local i, j, m, n, v;
n := Length(a);
v := List(a, Length);
m := Maximum(v);
for j in [1 .. m] do
f(List([1 .. n], i -> a[i][1 + RemInt(j - 1, v[i])]));
od;
end;
 
# Here we simply print each "row"
f := function(u)
Perform(u, Print);
Print("\n");
end;
 
Loop([["a", "b", "c"], ["A", "B", "C"], [1, 2, 3]], f);
 
aA1
bB2
cC3
 
Loop([["a", "b"], ["A", "B", "C", "D", "E"], [1, 2, 3]], f);
 
aA1
bB2
aC3
bD1
aE2

[edit] Go

Go's "range clause" of a for statement only looks at a single iterable value (array, slice, etc). To access the three in parallel, they have to be explicitly indexed.

If a2 or a3 were shorter, the program would panic with "runtime error: index out of range". If a2 or a3 were longer, extra elements would be ignored. Go's philosophy is that you should explicitly check for whatever conditions are meaningful in your application and explicitly handle whatever errors are plausible.

package main
 
import "fmt"
 
var a1 = []string{"a", "b", "c"}
var a2 = []byte{'A', 'B', 'C'}
var a3 = []int{1, 2, 3}
 
func main() {
for i := range a1 {
fmt.Printf("%v%c%v\n", a1[i], a2[i], a3[i])
}
}

[edit] Golfscript

["a" "b" "c"]:a;
["A" "B" "C"]:b;
["1" "2" "3"]:c;
[a b c]zip{puts}/

If there are arrays of different size, the shorter are treated as "null-padded" array.


[edit] Groovy

Solution:

def synchedConcat = { a1, a2, a3 ->
assert a1 && a2 && a3
assert a1.size() == a2.size()
assert a2.size() == a3.size()
[a1, a2, a3].transpose().collect { "${it[0]}${it[1]}${it[2]}" }
}

Test:

def x = ['a', 'b', 'c']
def y = ['A', 'B', 'C']
def z = [1, 2, 3]
 
synchedConcat(x, y, z).each { println it }
Output:
aA1
bB2
cC3

[edit] Haskell

main = mapM_ putStrLn $ zipWith3 (\a b c -> 
[a,b,c]) "abc" "ABC" "123"

zipWith (2 lists) and zipWith3

are exported by Prelude. zipWith4 through 

zipWith7 are available in the Data.List module.

If lists are different lengths, it stops after the shortest one.

[edit] Haxe

using Lambda;
using Std;
 
class Main
{
 
static function main()
{
var a = ['a', 'b', 'c'];
var b = ['A', 'B', 'C'];
var c = [1, 2, 3];
 
//Find smallest array
var len = [a, b, c]
.map(function(a) return a.length)
.fold(Math.min, 0x0FFFFFFF)
.int();
 
for (i in 0...len)
Sys.println(a[i] + b[i] + c[i].string());
}
}

[edit] HicEst

CHARACTER :: A = "abc"
REAL :: C(3)
 
C = $ ! 1, 2, 3
 
DO i = 1, 3
WRITE() A(i), "ABC"(i), C(i)
ENDDO

[edit] Icon and Unicon

The first solution uses co-expressions to produce parallel evaluation.

procedure main()
a := create !["a","b","c"]
b := create !["A","B","C"]
c := create !["1","2","3"]
while write(@a,@b,@c)
end

The second solution is more like other procedural languages and also handles unequal list lengths.

link numbers  # for max
 
procedure main()
 
a := ["a","b","c"]
b := ["A","B","C","D"]
c := [1,2,3]
 
every i := 1 to max(*a,*b,*c) do
write(a[i]|"","\t",b[i]|"","\t",c[i]|"")
end

[http://www.cs.arizona.edu/icon/library/procs/numbers.htm Uses max from numbers]

[edit] J

For arrays of different types:

   ,.&:(":"0@>)/ 'abc' ; 'ABC' ; 1 2 3
aA1
bB2
cC3

This approach works by representing the digits as characters.

Where arrays are all the same type (all numeric or all string):

   ,.&:>/ 'abc' ; 'ABC' ; '123'
aA1
bB2
cC3

Both of these implementations reject arrays with conflicting lengths.

Other options include:

   |: 'abc', 'ABC' ,:;":&> 1 2 3
aA1
bB2
cC3
   |: 'abc', 'ABC',: '123'
aA1
bB2
cC3

These implementations pad short arrays with spaces.

Or:

   |:>]&.>L:_1 'abc';'ABC';<1 2 3
┌─┬─┬─┐
│a│A│1
├─┼─┼─┤
│b│B│2
├─┼─┼─┤
│c│C│3
└─┴─┴─┘

This implementation puts each item from each of the original lists into a box and forms an array of boxes. (A "box" is a immutable pointer to immutable data -- in other words value semantics instead of reference semantics -- and "putting an item into a box" is obtaining one of these pointers for that item.) This implementation extends any short array by providing empty boxes to represent the missing elements. (An "empty box" is what a programmer in another language might call "a pointer to a zero length array".)

[edit] Java

Translation of: JavaScript
String[] a = {"a","b","c"};
String[] b = {"A","B","C"};
int[] c = {1,2,3};
for(int i = 0;i < a.length;i++){
System.out.println(a[i] + b[i] + c[i]);
}

If the first array is too short, it will stop when it gets to the end of the first array. If one of the other arrays is too short, an ArrayIndexOutOfBoundException will be thrown.

[edit] jq

The following solution is based on the assumption that all the arrays can be presented as an array of arrays. This allows any number of arrays to be handled.

Specifically, zip/0 expects an array of 0 or more arrays as its input. The first array determines the number of items in the output; nulls are used for padding.

# zip/0 emits [] if input is [].
 
def zip:
. as $in
| [range(0; $in[0]|length) as $i | $in | map( .[$i] ) ];

Example 1:

[["a","b","c"], ["A","B","C"], [1,2,3]] | zip
Output:
 [["a","A",1],["b","B",2],["c","C",3]]

To obtain the compact output used in the the task description, we can filter the results through a "pretty-print" function:

def pp: reduce .[] as $i (""; . + "\($i)");

Example 2:

[["a","b","c"], ["A","B","C"], [1,2,3]] | zip | map(pp)
Output:
 [
  "aA1",
  "bB2",
  "cC3"
 ]

As already mentioned, the above definition of zip/0 privileges the first

array, 

and if the subsequent arrays are of different lengths, null is used as a

filler. 

Thus:

[["a","b","c"], ["A","B"], [1]] | zip

produces:

[["a","A",1],["b","B",null],["c",null,null]]

Handling jagged input An alternative approach would be use a variant of zip/0 that pads all arrays shorter than the longest with nulls. Here is such a variant:

 
# transpose a possibly jagged matrix
def transpose:
if . == [] then []
else (.[1:] | transpose) as $t
| .[0] as $row
| reduce range(0; [($t|length), (.[0]|length)] | max) as $i
([]; . + [ [ $row[$i] ] + $t[$i] ])
end;
 

[edit] K

{,/$x}'+("abc";"ABC";1 2 3)
Output:
("aA1"
 "bB2"
 "cC3")    

If the length of the arrays are different, then K croaks with "length error".

The following is a more general approach where

 
&/#:'x
 

calculates the minimum length of the arrays and is used to index the first elements in each array.

 
{+x[;!(&/#:'x)]}("abc";"ABC";"1234")
 
Output:
("aA1"
 "bB2"
 "cC3")
 

If the arrays are of different type, then the arrays must be converted to strings.

 
{a:,/'($:'x);+a[;!(&/#:'a)]}("abc";"ABC";1 2 3 4)
 

[edit] JavaScript

This loops over the indices of the first array, and uses that to index into the others.

var a = ["a","b","c"],
b = ["A","B","C"],
c = [1,2,3],
output = "",
i;
for (i = 0; i < a.length; i += 1) {
output += a[i] + b[i] + c[i] + "\n";
}

If the b or c arrays are too "short", you will see the string "undefined" appear in the output.

[edit] Julia

With a higher order function:

julia> map(println, 
('a','b','c'),('A','B','C'),(1,2,3)) ;
aA1
bB2
cC3
 

With a loop:

julia> for (i,j,k) in 
zip(('a','b','c'),('A','B','C'),(1,2,3))
println(i,j,k)
end
aA1
bB2
cC3
 

[edit] LFE

 
(lists:zipwith3
(lambda (i j k)
(io:format "~s~s~p~n" `(,i ,j ,k)))
'(a b c)
'(A B C)
'(1 2 3))
 

If any of the data lists differ in size from the other, the results will print out up to the shortest data list, and then raise a function_clause error.

Erlang, and thus LFE, have zipwith and zipwith3 for working with 2 and 3 simultaneous sets of data respectively. If you need more than that, you'll need to create your own "zip" function with something like (: lists map ...).

[edit] Liberty BASIC

a$(1)="a" : a$(2)="b" : a$(3)="c"
b$(1)="A" : b$(2)="B" : b$(3)="C"
c(1)=1 : c(2)=2 : c(3)=3
 
 
for i = 1 to 3
print a$(i);b$(i);c(i)
next

[edit] Lisaac

Section Header
 
+ name := ARRAY_LOOP_TEST;
 
Section Public
 
- main <- (
+ a1, a2 : ARRAY[CHARACTER];
+ a3 : ARRAY[INTEGER];
 
a1 := ARRAY[CHARACTER].create 1 to 3;
a2 := ARRAY[CHARACTER].create 1 to 3;
a3 := ARRAY[INTEGER].create 1 to 3;
 
1.to 3 do { i : INTEGER;
a1.put ((i - 1 + 'a'.code).to_character) to i;
a2.put ((i - 1 + 'A'.code).to_character) to i;
a3.put i to i;
};
 
1.to 3 do { i : INTEGER;
a1.item(i).print;
a2.item(i).print;
a3.item(i).print;
'\n'.print;
};
);

[edit] LiveCode

Arrays

command loopArrays
local lowA, uppA, nums, z
put "a,b,c" into lowA
put "A,B,C" into uppA
put "1,2,3" into nums
 
split lowA by comma
split uppA by comma
split nums by comma
 
repeat with n = 1 to the number of elements of lowA
put lowA[n] & uppA[n] & nums[n] & return after z
end repeat
put z
 
end loopArrays

"list" processing

command loopDelimitedList
local lowA, uppA, nums, z
put "a,b,c" into lowA
put "A,B,C" into uppA
put "1,2,3" into nums
 
repeat with n = 1 to the number of items of lowA
put item n of lowA & item n of uppA & item n of nums
& return after z
end repeat
put z
 
end loopDelimitedList

Output - both behave similarly for this exercise.

aA1
bB2
cC3

When there are fewer elements than the first (or whatever the loop is based on), livecode will add an "empty" value. If we add a "d" to lowA and a 4 to nums we get the following:

aA1
bB2
cC3
d4

[edit]

Works with: UCB Logo
show (map [(word ?1 ?2 ?3)] [a b c] [A B C] [1 2 3])   
 ; [aA1 bB2 cC3]
 
(foreach [a b c] [A B C] [1 2 3] [print (word ?1 ?2 ?3)])  ; as above,
one per line

[edit] Lua

This can be done with a simple for loop:

 
a1, a2, a3 = {a , b , c } , { A , B , C } , { 1 , 2 , 3 }
for i = 1, 3 do print(a1[i],a2[i],a3[i]) end
 

but it may be more enlightening (and in line with the spirit of the challenge) to use the generic for:

 
function iter(a, b, c)
local i = 0
return function()
i = i + 1
return a[i], b[i], c[i]
end
end
 
for u, v, w in iter(a1, a2, a3) do print(u, v, w) end
 

[edit] Mathematica

This can be done with a built-in function:

 
MapThread[Print, {{"a", "b", "c"}, {"A", "B", "C"}, {1, 2, 3}}];
 

All arguments must be lists of the same length.

[edit] Mercury

 
:- module multi_array_loop.
:- interface.
 
:- import_module io.
:- pred main(io::di, io::uo) is det.
 
:- implementation.
:- import_module char, list, string.
 
main(!IO) :-
A = ['a', 'b', 'c'],
B = ['A', 'B', 'C'],
C = [1, 2, 3],
list.foldl_corresponding3(print_elems, A, B, C, !IO).
 
:- pred print_elems(char::in, char::in, int::in, io::di, io::uo) is det.
 
print_elems(A, B, C, !IO) :-
io.format("%c%c%i\n", [c(A), c(B), i(C)], !IO).
 

The foldl_corresponding family of procedures all throw a software_error/1 exception if the lengths of the lists are not the same.

[edit] Modula-3

MODULE MultiArray EXPORTS Main;
 
IMPORT IO, Fmt;
 
TYPE ArrIdx = [1..3];
 
VAR
arr1 := ARRAY ArrIdx OF CHAR {'a', 'b', 'c'};
arr2 := ARRAY ArrIdx OF CHAR {'A', 'B', 'C'};
arr3 := ARRAY ArrIdx OF INTEGER {1, 2, 3};
 
BEGIN
FOR i := FIRST(ArrIdx) TO LAST(ArrIdx) DO
IO.Put(Fmt.Char(arr1[i]) & Fmt.Char(arr2[i]) &
Fmt.Int(arr3[i]) & "\n");
END;
END MultiArray.

[edit] MUMPS

Pieces of String version

 
LOOPMULT
N A,B,C,D,%
S A="a,b,c,d"
S B="A,B,C,D"
S C="1,2,3"
S D=","
F %=1:1:$L(A,",") W !,$P(A,D,%),$P(B,D,%),$P(C,D,%)
K A,B,C,D,%
Q
 

When there aren't enough elements, a null string will be returned from the $Piece function.

Output:
USER>d LOOPMULT^ROSETTA
 
aA1
bB2
cC3
dD

Local arrays version

 
LOOPMULU
N A,B,C,D,%
S A(1)="a",A(2)="b",A(3)="c",A(4)="d"
S B(1)="A",B(2)="B",B(3)="C",B(4)="D"
S C(1)="1",C(2)="2",C(3)="3"
 ; will error S %=$O(A("")) F Q:%="" W !,A(%),B(%),C(%) S
%=$O(A(%))
S %=$O(A("")) F Q:%="" W !,$G(A(%)),$G(B(%)),$G(C(%)) S %=$O(A(%))
K A,B,C,D,%
 

The commented out line will throw an <UNDEFINED> error when trying

to look up D(4). Using the $Get function as a wrapper means that if the
subscript for the array doesn't exist, a null string will be returned. 

This same syntax is used for globals (permanent variables, that have a caret "^" as the first character).

Output:
USER>D LOOPMULU^ROSETTA
 
aA1
bB2
cC3
dD
USER>D LOOPMULV^ROSETTA

aA1
bB2
cC3
dD
 S %=$O(A("")) F  Q:%=""  W !,A(%),B(%),C(%) S %=$O(A(%))
                                        ^
<UNDEFINED>LOOPMULV+5^ROSETTA *C(4)

[edit] Nemerle

It "feels" better to use zip() for this, unfortunately the built in zip() only takes two lists.

using System;
using System.Console;
 
module LoopMultiple
{
Zip3[T1, T2, T3] (x : list[T1], y : list[T2], z : list[T3]) :
list[T1 * T2 * T3]
{
|(x::xs, y::ys, z::zs) => (x, y, z)::Zip3(xs, ys, zs)
|([], [], []) => []
|(_, _, []) => throw ArgumentNullException()
|(_, [], _) => throw ArgumentNullException()
|([], _, _) => throw ArgumentNullException()
}
 
Main() : void
{
def first = ['a', 'b', 'c'];
def second = ["A", "B", "C"];
def third = [1, 2, 3];
 
foreach ((x, y, z) in Zip3(first, second, third))
WriteLine($"$x$y$z");
}
}
Alternately:
Translation of: C#
using System.Console;
 
module LoopMult
{
Main() : void
{
def first = array['a', 'b', 'c'];
def second = array['A', 'B', 'C'];
def third = array[1, 2, 3];
 
when (first.Length == second.Length && second.Length ==
third.Length)
foreach (i in [0 .. (first.Length - 1)])
WriteLine("{0}{1}{2}", first[i], second[i], third[i]);
}
}

[edit] NetRexx

/* NetRexx */
options replace format comments java crossref savelog symbols nobinary
 
say 'Using arrays'
aa = ['a', 'b', 'c', 'd']
bb = ['A', 'B', 'C']
cc = [1, 2, 3, 4]
 
loop x_ = 0 for aa.length
do
ax = aa[x_]
catch ArrayIndexOutOfBoundsException
ax = ' '
end
do
bx = bb[x_]
catch ArrayIndexOutOfBoundsException
bx = ' '
end
do
cx = cc[x_]
catch ArrayIndexOutOfBoundsException
cx = ' '
end
 
say ax || bx || cx
end x_
 
say 'Using indexed strings (associative arrays)'
ai = sampleData('a b c d')
bi = sampleData('A B C')
ci = sampleData('1 2 3 4')
 
loop x_ = 1 to ai[0]
say ai[x_] || bi[x_] || ci[x_]
end x_
 
method sampleData(arg) public static returns Rexx
smp = ' '
smp[0] = arg.words
loop i_ = 1 to smp[0]
smp[i_] = arg.word(i_)
end i_
 
return smp
 
Output:
Using arrays
aA1
bB2
cC3
d 4
Using indexed strings (associative arrays)
aA1
bB2
cC3
d 4

[edit] NewLISP

(map println '(a b c) '(A B C) '(1 2 
3))

[edit] Nim

let
a = @['a','b','c']
b = @["A","B","C"]
c = @[1,2,3]
 
for i in 0..2:
echo a[i], b[i], c[i]

[edit] Oberon-2

Works with oo2c version 2

 
MODULE LoopMArrays;
IMPORT
Out;
VAR
x,y: ARRAY 3 OF CHAR;
z: ARRAY 3 OF INTEGER;
 
PROCEDURE DoLoop;
VAR
i: INTEGER;
BEGIN
i := 0;
WHILE i < LEN(x) DO
Out.Char(x[i]);Out.Char(y[i]);Out.LongInt(z[i],0);Out.Ln;
INC(i)
END
END DoLoop;
 
BEGIN
x[0] := 'a';y[0] := 'A';z[0] := 1;
x[1] := 'b';y[1] := 'B';z[1] := 2;
x[2] := 'c';y[2] := 'C';z[2] := 3;
DoLoop
END LoopMArrays.
 

Output:

aA1
bB2
cC3

[edit] Objeck

 
class MultipleArrayAccess {
function : Main(args : String[]) ~ Nil {
a := ["a", "b", "c"];
b := ["A", "B", "C"];
c := [1, 2, 3];
 
each(i : a) {
a[i]->Append(b[i]);
a[i]->Append(c[i]);
a[i]->PrintLine();
};
}
}
 

If the arrays are different lengths, then an out-of-bounds error will be raised.

[edit] OCaml

an immediate solution:

let a1 = [| 'a'; 'b'; 'c' |]
and a2 = [| 'A'; 'B'; 'C' |]
and a3 = [| '1'; '2'; '3' |] ;;
 
Array.iteri (fun i c1 ->
print_char c1;
print_char a2.(i);
print_char a3.(i);
print_newline()
) a1 ;;

a more generic solution could be to use a function which iterates over a list of arrays:

let n_arrays_iter ~f = function
| [] -> ()
| x::xs as al ->
let len = Array.length x in
let b = List.for_all (fun a -> Array.length a = len) xs in
if not b then invalid_arg "n_arrays_iter: arrays of different
length"
;
for i = 0 to pred len do
let ai = List.map (fun a -> a.(i)) al in
f ai
done

this function raises Invalid_argument exception if arrays have different

length, 

and has this signature:

val n_arrays_iter : f:('a list -> unit) -> 'a 
array list -> unit

how to use it with arrays a1, a2 and a3 defined before:

let () =
n_arrays_iter [a1; a2; a3] ~f:(fun l ->
List.iter print_char l;
print_newline());
;;

[edit] Oforth

If arrays don't have the same size, zipAll reduces to the minimum size

[ "a", "b", "c" ] [ "A", "B", "C" ] [ 1, 2, 3 ] 
zipAll(3) apply(#[ apply(#print) printcr ])
Output:
aA1
bB2
cC3

[edit] ooRexx

 
x = .array~of("a", "b", "c")
y = .array~of("A", "B", "C")
z = .array~of(1, 2, 3)
 
loop i = 1 to x~size
say x[i]y[i]z[i]
end
 

[edit] Oz

for
I in [a b c]
J in ['A' 'B' 'C']
K in [1 2 3]
do
{System.showInfo I#J#K}
end

The loop will stop when the shortest list is exhausted.

[edit] PARI/GP

This version stops when the shortest vector is exhausted.

loopMultiple(V)={
my(l=#V[1]);
for(i=2,#V,l=min(l,#V[i]));
for(i=1,#V[1],
for(j=1,#V,
print1(V[j][i])
);
print()
)
};

This version prints blanks when a vector is exhausted.

loopMultiple(V)={
my(l=0);
for(i=1,#V,l=max(l,#V[i]));
for(i=1,#V[1],
for(j=1,#V,
if(#V[j]<i,
print1(" ")
,
print1(V[j][i])
)
);
print()
)
};

[edit] Pascal

See Delphi

[edit] Perl

sub zip (&@)
{
my $code = shift;
my $min;
$min = $min && $#$_ > $min ? $min : $#$_ for @_;
 
for my $i(0..$min){ $code->(map $_->[$i] ,@_) }
}
my @a1 = qw( a b c );
my @a2 = qw( A B C );
my @a3 = qw( 1 2 3 );
 
zip { print @_,"\n" }\(@a1, @a2, @a3);

This implementation will stop producing items when the shortest array ends.

[edit] Perl 6

Works with: niecza version 2011.07
for <a b c> Z <A B C> Z 1, 2, 3 -> $x, 
$y, $z {
say $x, $y, $z;
}

The Z operator stops emitting items as soon as the shortest input list is exhausted. However, short lists are easily extended by replicating all or part of the list, or by appending any kind of lazy list generator to supply default values as

necessary.

Note that we can also factor out the concatenation by making the Z metaoperator apply the ~ concatenation operator across each triple:

for <a b c> Z~ <A B C> Z~ 1, 2, 3 -> 
$line {
say $line;
}

We could also use the zip-to-string with the reduction metaoperator:

.say for [Z~] [<a b c>], [<A B C>], 
[1,2,3]

[edit] PHP

$a = array('a', 'b', 'c');
$b = array('A', 'B', 'C');
$c = array('1', '2', '3'); //These don't *have* to be strings, but it
saves PHP from casting them later
 
if ((sizeOf($a) !== sizeOf($b)) || (sizeOf($b) !== sizeOf($c))){
throw new Exception('All three arrays must be the same length');
}
foreach ($a as $key => $value){
echo "{$a[$key]}{$b[$key]}{$c[$key]}\n";
}

This implementation throws an exception if the arrays are not all the same length.

[edit] PicoLisp

(mapc prinl
'(a b c)
'(A B C)
(1 2 3) )

The length of the first argument list controls the operation. If subsequent lists are longer, their remaining values are ignored. If they are shorter, NIL is passed to the function.

[edit] PL/I

 
declare P(3) character (1) initial ('a', b', 'c'),
Q(3) character (1) initial ('A', 'B', 'C'),
R(3) fixed decimal (1) initial (1, 2, 3);
 
do i = lbound(P,1) to hbound(P,1);
put skip edit (P(i), Q(i), R(i)) (2 A, F(1));
end;
 

[edit] PostScript

Library: initlib
 
% transpose is defined in initlib like this.
/transpose {
[ exch {
{ {empty? exch pop} map all?} {pop exit} ift
[ exch {} {uncons {exch cons} dip exch} fold counttomark 1 roll]
uncons
} loop ] {reverse} map
}.
 
% using it.
[[/a /b /c] [/A /B /C] [1 2 3]] transpose
 

[edit] PowerBASIC

FUNCTION PBMAIN () AS LONG
DIM x(2), y(2) AS STRING * 1
DIM z(2) AS LONG
 
'data
ARRAY ASSIGN x() = ("a", "b", "c")
ARRAY ASSIGN y() = ("A", "B", "C")
ARRAY ASSIGN z() = (1, 2, 3)
 
'set upper bound
C& = UBOUND(x)
IF UBOUND(y) > C& THEN C& = UBOUND(y)
IF UBOUND(z) > C& THEN C& = UBOUND(z)
 
OPEN "output.txt" FOR OUTPUT AS 1
FOR L& = 0 TO C&
IF L& <= UBOUND(x) THEN PRINT #1, x(L&);
IF L& <= UBOUND(y) THEN PRINT #1, y(L&);
IF L& <= UBOUND(z) THEN PRINT #1, TRIM$(STR$(z(L&)));
PRINT #1,
NEXT
CLOSE
END FUNCTION

[edit] Prolog

Works with SWI-Prolog

multiple_arrays(L1, L2, L3) :-
maplist(display, L1, L2, L3).
 
display(A,B,C) :-
writef('%s%s%s\n', [[A],[B],[C]]).
 
Output:
 ?- multiple_arrays("abc", "ABC", "123").
aA1
bB2
cC3
true.

 ?- multiple_arrays("abc", "AB", "123").
aA1
bB2
false.

[edit] PureBasic

OpenConsole()
; Fill arrays
Dim a.s(2)
Dim b.s(2)
Dim c(2)
For Arrayposition = 0 To ArraySize(a())
a(Arrayposition) = Chr(Asc("a") + Arrayposition)
b(Arrayposition) = Chr(Asc("A") + Arrayposition)
c(Arrayposition) = Arrayposition + 1
Next
; loop over them
For Arrayposition = 0 To ArraySize(a())
PrintN(a(Arrayposition) + b(Arrayposition) + Str(c(Arrayposition)))
Next
Input() ;wait for Enter before ending

If they have different lengths there are two cases:
a() is the shortest one: Only elements up to maximum index of a() are printed
a() is bigger than another one: if exceeding index to much, program crashes,
else it may work because there is some "free space" after end of assigned array memory.
For example if a has size 4, line dD4 will also be printed. size 20 leads to an crash
This is because ReDim becomes slow if everytime there is a change to array size new memory has to be allocated.

[edit] Python

Using zip():

>>> print ( '\n'.join(''.join(x) for x in 
zip('abc', 'ABC', '123')) )
aA1
bB2
cC3
>>>

If lists are different lengths, zip() stops after the shortest one.

Using map():

>>> print ( '\n'.join(map(lambda *x: 
''.join(x), 'abc', 'ABC', '123')) )
aA1
bB2
cC3
>>>

If lists are different lengths, map() in Python 2.x

pretends that the shorter lists were extended with 

None items; map() in Python 3.x stops after the shortest one.

Using itertools.imap() (Python 2.x):

from itertools import imap
 
def join3(a,b,c):
print a+b+c
 
imap(join3,'abc','ABC','123')

If lists are differnt lengths, imap() stops after the shortest is exhausted.

[edit] zip_longest

Python 3.X has zip_longest which fills shorter iterables with its fillvalue argument which defaults to None (similar to the behavior of map() in Python 2.x):

>>> from itertools import zip_longest
>>> print ( '\n'.join(''.join(x) for x in zip_longest('abc',
'ABCD', '12345', fillvalue='#')) )
aA1
bB2
cC3
#D4
##5
>>>

(The Python 2.X equivalent is itertools.izip_longest)

[edit] R

multiloop <- function(...)
{
# Retrieve inputs and convert to a list of character strings
arguments <- lapply(list(...), as.character)
 
# Get length of each input
lengths <- sapply(arguments, length)
 
# Loop over elements
for(i in seq_len(max(lengths)))
{
# Loop over inputs
for(j in seq_len(nargs()))
{
# print a value or a space (if that input has finished)
cat(ifelse(i <= lengths[j], arguments[[j]][i], " "))
}
cat("\n")
}
}
multiloop(letters[1:3], LETTERS[1:3], 1:3)

Same thing as a single function call. But throws error if the arrays differ in length.

 
apply(data.frame(letters[1:3], LETTERS[1:3], 1:3), 1,
function(row) { cat(row, "\n", sep='') })
 

[edit] Racket

Racket for loops can loop over an arbitrary number of sequences at once:

 
#lang racket
 
(for ([i-1 '(a b c)]
[i-2 '(A B C)]
[i-3 '(1 2 3)])
(printf "~a ~a ~a~n" i-1 i-2 i-3))
 

[edit] REXX

[edit] same size arrays

If any of the array's elements are missing or it is a short list, a blank is substituted to retain visual fidelity in the output.

When all elements are blank, then it signifies the end of the arrays.

/*REXX program shows how to  simultaneously  loop over 
multiple arrays.*/

x. = ' '; x.1 = "a"; x.2 = 'b'; x.3 = "c"
y. = ' '; y.1 = "A"; y.2 = 'B'; y.3 = "C"
z. = ' '; z.1 = "1"; z.2 = '2'; z.3 = "3"
 
do j=1 until output=''
output = x.j || y.j || z.j
say output
end /*j*/ /*stick a fork in it, we're
done.*/
Output:
aA1
bB2
cC3

[edit] dissimilar sized arrays

In this example, two of the arrays are extended (past the 1st example).
Also note that REXX doesn't require quotes around numbers (they're optional).

/*REXX program shows how to  simultaneously  loop over 
multiple arrays.*/

x.=' '; x.1="a"; x.2='b'; x.3="c"; x.4='d'
y.=' '; y.1="A"; y.2='B'; y.3="C";
z.=' '; z.1= 1 ; z.2= 2 ; z.3= 3 ; z.4= 4; z.5=
5
 
do j=1 until output=''
output=x.j || y.j || z.j
say output
end /*j*/ /*stick a fork in it, we're
done.*/
Output:
aA1
bB2
cC3
d 4
  5

[edit] dissimilar sized lists

/*REXX program shows how to  simultaneously  loop over 
multiple lists.*/

x = 'a b c d'
y = 'A B C'
z = 1 2 3 4
do j=1 until output=''
output = word(x,j) || word(y,j) || word(z,j)
say output
end /*j*/ /*stick a fork in it, we're
done.*/
Output:
aA1
bB2
cC3
d4

[edit] idiomatic method for lists

/*REXX program shows how to  simultaneously  loop over 
multiple lists.*/

x = 'a b c d'
y = 'A B C'
z = 1 2 3 4 ..LAST
do j=1 for max(words(x), words(y), words(z))
say word(x,j) || word(y,j) || word(z,j)
end /*j*/ /*stick a fork in it, we're
done.*/
Output:
aA1
bB2
cC3
d4
..LAST

[edit] Ruby

['a','b','c'].zip(['A','B','C'], [1,2,3]) {|i,j,k| puts
"#{i}#{j}#{k}"}

or

['a','b','c'].zip(['A','B','C'], [1,2,3]) {|a| puts 
a.join}

Both of these loops print aA1, bB2, cC3.

Array#zip iterates once for each element of the

receiver.  

If an argument array is longer, the excess elements are ignored. If an argument array is shorter, the value nil is supplied.

[edit] Run BASIC

for i = 1 to 3
a$(i) = chr$(i+96)
b$(i) = chr$(i+64)
c(i) = i
next i
 
for i = 1 to 3
print a$(i);b$(i);c(i)
next

[edit] Rust

// rust 0.9-pre
 
fn main() {
let a1 = ["a", "b", "c"];
let a2 = ["A", "B", "C"];
let a3 = [1, 2, 3];
 
for ((&x, &y), &z) in
a1.iter().zip(a2.iter()).zip(a3.iter()) {
println!("{}{}{}", x, y, z);
}
}
Output:
aA1
bB2
cC3

[edit] Salmon

// First, we'll define a general-purpose zip() to zip
any
// number of lists together.
function zip(...)
{
variable result;
variable list_num := 0;
iterate(arg; arguments)
{
variable elem_num := 0;
iterate (x; arg)
{
result[elem_num][list_num] := x;
++elem_num;
};
++list_num;
};
return result;
};
 
immutable a := ["a", "b", "c"],
b := ["A", "B", "C"],
c := [1, 2, 3];
iterate (x; zip(a, b, c))
print(x[0], x[1], x[2], "\n");;

The preceding code will throw an exception if the lists aren't the same length. Here's an example that will print a number of lines equal to the length of the longest list and print nothing for elements that are missing if some lists are shorter than the longest:

// First, we'll define a general-purpose zip() to zip
any
// number of lists together.
function zip(...)
{
variable result := [];
variable list_num := 0;
iterate(arg; arguments)
{
variable elem_num := 0;
iterate (x; arg)
{
if (elem_num >= length(result))
result[elem_num] := <<(* --> "")>>;;
result[elem_num][list_num] := x;
++elem_num;
};
++list_num;
};
return result;
};
 
immutable a := ["a", "b", "c"],
b := ["A", "B", "C"],
c := [1, 2, 3];
iterate (x; zip(a, b, c))
print(x[0], x[1], x[2], "\n");;

[edit] Sather

class MAIN is
main is
a :ARRAY{STR} := |"a", "b", "c"|;
b :ARRAY{STR} := |"A", "B", "C"|;
c :ARRAY{STR} := |"1", "2", "3"|;
loop i ::= 0.upto!(2);
#OUT + a[i] + b[i] + c[i] + "\n";
end;
end;
end;

If the index i is out of bounds, a runtime error is raised.

[edit] Scala

 
("abc", "ABC", "123").zipped foreach { (x, y, z) =>
println(x.toString + y + z)
}
 

[edit] Scheme

Scheme provides for-each and map to iterate a function over one or more lists. The map form is used to collect the results into a new list.

 
(let ((a '("a" "b" "c"))
(b '("A" "B" "C"))
(c '(1 2 3)))
(for-each
(lambda (i1 i2 i3)
(display i1)
(display i2)
(display i3)
(newline))
a b c))
 

Scheme has a vector datatype with constant-time

retrieval of items held in an ordered sequence.  Use srfi-43 to get 

similar iterators for vectors, vector-for-each and vector-map:

 
(let ((a (vector "a" "b" "c"))
(b (vector "A" "B" "C"))
(c (vector 1 2 3)))
(vector-for-each
(lambda (current-index i1 i2 i3)
(display i1)
(display i2)
(display i3)
(newline))
a b c))
 

Note, the lists or vectors must all be of the same length.

[edit] Sidef

The simplest way is to use MultiArrays:

MultiArray.new(%w(a b c),%w(A B C),%w(1 2 3)).each { 
|i,j,k|
say "#{i}#{j}#{k}";
};

Another approach is to zip two arrays at a time and reduce pairs of their elements into one element.

func multi_zip(zipped) {
.each { |arr|
zipped.zip!(arr).reducePairs!{.flatten};
};
return zipped;
}
 
multi_zip(%w(a b c),%w(A B C),%w(1 2 3)).each{ |i,j,k|
say "#{i}#{j}#{k}";
};

The returned array will have the same number of elements as the shortest

array.

[edit] Standard ML

The below code will combine arbitrarily many lists of strings into a single list with length equal to that of the shortest list.

 
(*
* val combine_lists : string list list -> string list
*)
fun combine_lists nil = nil
| combine_lists (l1::ls) = List.foldl (ListPair.map (fn (x,y) => y ^
x)) l1 ls;
 
(* ["a1Ax","b2By","c3Cz"] *)
combine_lists[["a","b","c"],["1","2","3"],["A","B","C"],["x","y","z"]];
 

[edit] Smalltalk

Works with: GNU Smalltalk
|a b c|
a := OrderedCollection new addAll: #('a' 'b' 'c').
b := OrderedCollection new addAll: #('A' 'B' 'C').
c := OrderedCollection new addAll: #(1 2 3).
 
1 to: (a size) do: [ :i |
(a at: i) display.
(b at: i) display.
(c at: i) displayNl.
].

If index i is out of bound, a runtime error is raised.

[edit] SuperCollider

([\a,\b,\c]+++[\A,\B,\C]+++[1,2,3]).do({|array| 
array.do(_.post); "".postln })

[edit] Swift

let a1 = ["a", "b", "c"]
let a2 = ["A", "B", "C"]
let a3 = [1, 2, 3]
 
for i in 0 ..< a1.count {
println("\(a1[i])\(a2[i])\(a3[i])")
}
Output:
aA1
bB2
cC3

[edit] Tcl

set list1 {a b c}
set list2 {A B C}
set list3 {1 2 3}
foreach i $list1 j $list2 k $list3 {
puts "$i$j$k"
}

If lists are different lengths, the manual [1] says: "The total number of loop iterations is large enough to use up all the values from all the value lists. If a value list does not contain enough elements for each of its loop variables in each iteration, empty values are used for the missing elements."

[edit] TorqueScript

 
$var[0] = "a b c"
$var[1] = "A B C";
$var[2] = "1 2 3";
 
for(%i=0;%i<3;%i++)
echo(getWord($var[0],%i) @ getWord($var[1],%i) @ getWord($var[2],%i));
 

[edit] TUSCRIPT

 
$$ MODE TUSCRIPT
arr1="a'b'c"
arr2="a'b'C"
arr3="1'2'3"
LOOP a=arr1,b=arr2,c=arr3
PRINT a,b,c
ENDLOOP
 
Output:
aa1
bb2
cC3

[edit] TXR

[edit] Pattern language

$ txr -c '@(bind a ("a" "b" "c"))
@(bind b ("A" "B" "C"))
@(bind c ("1" "2" "3"))
@(output)
@ (repeat)
@a@b@c
@ (end)
@(end)'

aA1
bB2
cC3

[edit] TXR Lisp, using mapcar

Here we actually loop over four things: three strings and an infinite list of newlines. The output is built up as one string object that is finally printed in one go.

$ txr -e '(pprint (mappend (op list) "abc" "ABC" "123" 
(repeat "\n"))))'

aA1
bB2
cC3

[edit] TXR Lisp, using each

$ txr -e '(each ((x "abc") (y "ABC") (z "123")) 
(put-line `@x@y@z`))'

aA1
bB2
cC3

[edit] Translation of Scheme

Translation of: Scheme

No "srfi-43" required:

@(do
 ;; Scheme's vector-for-each: a one-liner in TXR
 ;; that happily works over strings and lists.
(defun vector-for-each (fun . vecs)
[apply mapcar fun (range) vecs])
 
(defun display (obj : (stream *stdout*))
(pprint obj stream))
 
(defun newline (: (stream *stdout*))
(display #\newline stream))
 
(let ((a (vec "a" "b" "c"))
(b (vec "A" "B" "C"))
(c (vec 1 2 3)))
(vector-for-each
(lambda (current-index i1 i2 i3)
(display i1)
(display i2)
(display i3)
(newline))
a b c)))

[edit]

Translation of: Logo
@(do
(macro-time
(defun question-var-to-meta-num (var)
^(sys:var ,(int-str (cdr (symbol-name var))))))
 
(defmacro map (square-fun . square-args)
(tree-bind [(fun . args)] square-fun
^[apply mapcar (op ,fun ,*[mapcar question-var-to-meta-num args])
(macrolet ([(. args) ^(quote ,args)])
(list ,*square-args))]))
 
(defun word (. items)
[apply format nil "~a~a~a" items])
 
(defun show (x) (pprinl x))
 
(show (map [(word ?1 ?2 ?3)] [a b c] [A B C] [1 2 3])))
Output:
(aA1 bB2 cC3)

[edit] UNIX Shell

With the Bourne shell, its for loop (from Loops/Foreach#UNIX Shell) can iterate only one list. We use an index i to access the other lists: set -- $list loads the positional parameters, and shift $i moves our element to $1.

Works with: Bourne Shell
a=a:b:c
b=A:B:C
c=1:2:3
 
oldifs=$IFS
IFS=:
i=0
for wa in $a; do
set -- $b; shift $i; wb=$1
set -- $c; shift $i; wc=$1
 
printf '%s%s%s\n' $wa $wb $wc
 
i=`expr $i + 1`
done
IFS=$oldifs
Output:
aA1
bB2
cC3

When the lists have different lengths, this code uses the length of list

a. Longer lists ignore their extra elements, 

and shorter lists give extra empty strings.


Inspired by the previous example, below is the way to loop over two arrays simultaneously using set -- $ARGS. It is less general than the previous example but it is shorter and works just fine.

Works with: Bourne Shell
A='a1 a2 a3'
B='b1 b2 b3'
 
set -- $B
for a in $A
do
printf "$a $1\n"
shift
done
Output:
a1 b1
a2 b2
a3 b3


Some shells have real arrays, so the iteration is much more simple and easy.

Works with: bash
Works with: ksh93
a=(a b c)
b=(A B C)
c=(1 2 3)
for ((i = 0; i < ${#a[@]}; i++)); do
echo "${a[$i]}${b[$i]}${c[$i]}"
done
Output:
aA1
bB2
cC3
Works with: ksh93
Works with: pdksh
set -A a a b c
set -A b A B C
set -A c 1 2 3
((i = 0))
while ((i < ${#a[@]})); do
echo "${a[$i]}${b[$i]}${c[$i]}"
((i++))
done
Works with: zsh
a=(a b c)
b=(A B C)
c=(1 2 3)
for ((i = 1; i <= $#a; i++)); do
echo "$a[$i]$b[$i]$c[$i]"
done

[edit] C Shell

Uses the length of array a. Longer arrays ignore their extra elements, but shorter arrays force the shell to exit with an error like b: Subscript out of range.

set a=(a b c)
set b=(A B C)
set c=(1 2 3)
@ i = 1
while ( $i <= $#a )
echo "$a[$i]$b[$i]$c[$i]"
@ i += 1
end

[edit] Ursala

Compute the transpose of the list formed of the three lists. If they're of unequal lengths, an exception occurs.

#show+
 
main = ~&K7 <'abc','ABC','123'>
Output:
aA1
bB2
cC3

[edit] Wart

each (x X n) (zip '(a b c) '(A B C) '(1 2 3))
prn x X n

[edit] XPL0

string 0;               \use zero terminated strings
include c:\cxpl\codes; \intrinsic 'code' declarations
char A1, A2;
int A3, I;
[A1:= "abc";
A2:= "ABC";
A3:= [1,2,3];
for I:= 0 to 2 do
[ChOut(0, A1(I));
ChOut(0, A2(I));
IntOut(0, A3(I));
CrLf(0);
];
]
Output:
aA1
bB2
cC3

[edit] zkl

Utils.zipWith(False,fcn{vm.arglist.concat().println()},
["a".."c"],T("A","B","C"),[1..])
Output:
aA1
bB2
cC3

zipWith stops at the end of the shortest sequence, which means it can work with infinite sequences

[edit] ZX Spectrum Basic

10 LET sza = 3: REM size of a
20 LET szb = 3: REM size of b
30 LET szc = 3: REM size of c
40 DIM a$(sza): DIM b$(szb): DIM c$(szc)
50 LET max = sza: REM assume a is the biggest
60 IF szb > max THEN LET max = szb: REM now try b
70 IF szc > max THEN LET max = szc: REM or c
80 REM populate our arrays, and as a bonus we already have our demo loop
90 REM we might as well print as we populate showing the arrays in
columns
100 FOR l = 1 TO max
110 IF l <= sza THEN READ a$(l): PRINT a$(l);
120 IF l <= szb THEN READ b$(l): PRINT b$(l);
130 IF l <= szc THEN READ c$(l): PRINT c$(l);
140 PRINT: REM newline
150 NEXT l
150 PRINT "The arrays are shown in columns."
160 PRINT "A$ runs down the left hand side,"
170 PRINT "and C$ runs down the right."
180 STOP
200 DATA "a","b","c","A","B","C","1","2","3"

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