Reinvent the For loop [closed]

Question

For loops are used extensively in many languages, but what would you do if no languages supported them?

Create a way to execute a basic for loop without using any repetition structures (for, foreach, while, do, etc).

The basic for loop that you need to replicate is set up like this

for(i=0;i<1000;i++)

You must be able to replicate this without using repetition structures. It must also execute code in your language that would be in the body of the loop. Any form of eval is allowed, though it may not execute the for loop on its own.

You can test your code by having it print i with a space 100 times, add this test case to the end of your answer to verify your code with others.

There are no restrictions on what exactly it has to be, all it needs to do is replicate the for loop.

Winner will be decided based on upvotes at the time that it is chosen.

Answer 1

Windows Batch File, 65

set I=%S%
:l
if %I% GEQ %E% goto :eof
call %C%
set /a I+=1
goto l

Test file:

@echo off
set S=0
set E=100
set "C=<nul set /p X=%%I%% "
call for.cmd

Can save two bytes if the loop always starts at 0.

Answer 2

Perl (23 chars.):

print join " ",(0..999);*

or same Perl but in simpler yet more lengthy and recursive words:

sub i {($s,$e)=@_; return if $s==$e; print "$s "; i($s+1,$e)}

i(0,1000);

Answer 3

C#, 70 chars

Enumerable.Range(0,999).ToList().ForEach(x=>Console.WriteLine(x+" "));

This can probably be golfed down, but it's the best I could come up with quickly.

Answer 4

QuickBASIC, 103 characters

10 IF i < 1000 THEN PRINT MID$(STR$(i) + SPACE$(1), 2, ABS(i < 100) * 5); : i = i + 1: GOTO 10 ELSE END

Answer 5

Java with Lambda — 259 characters

I just built the prerelease Java langtools with the experimental lambda support that has recently been canceled for JDK 7 and pushed back until JDK 8 in 2012 (boo!) and wanted to try it out.

Formatted nicely, this version clocks in at 304 characters. If you reformat it so all the code of the interface is on one line and the class is on another, it gets down to 259 characters. I'm sure you could golf it down lower (shorten the identifiers, for starters), but Java is never going to be competitive at golf, so why obfuscate it.

interface Fore {
    void exec(int i);
}

public class ForLoop {
    public static void main(String[] args) {
        loop(1, 10, #{ int i -> System.out.println(i) });
    }

    public static void loop(int x, int max, Fore fore) {
        fore.exec(x);
        if (x < max) loop(x+1, max, fore);
    }
}

I just wanted to demonstrate what will be possible with lambdas in Java SE 8. The call to loop could be written with an anonymous inner class, instead:

loop(1, 10, new Fore() {
    public void exec(int i) {
        System.out.println(i);
    }
});

Yuck.

The syntax for lambdas in Java hasn't been settled yet; this is just what works with the current dev build of javac. Thanks to those who are working to make it happen. Java should have gotten lambdas and closures years ago. Alas.

Answer 6

C

(not really golfing, but fun)

#include <setjmp.h>
#include <stdio.h>

int main() {
    jmp_buf b;
    int i;
    if ((i = setjmp(b)) < 100) {
        printf("%d\n", i);
        longjmp(b, i + 1); 
    }
} 

Answer 7

JavaScript, 63 characters

(function i(s,r){r+=s+' ';s++<1e3?i(s,r):console.log(r)})(0,'')

with proper console output

Answer 8

R - 11 characters

General case:

f(1:1000)

Where f is your function.

Specific case:

cat(1:1000)

Answer 9

C 45 characters including printout

Compiles, links, and runs as-is; no need to define a separate function and then call it, adding to source size.

main(a){printf("%d ",a-1);a<1000&&main(a+1);}

Answer 10

Javascript (44 chars.):

Another rather pointless option, but then who said golf had to have a point :) Plus I gained something new... I never realised you could get away with i+++

eval(Array((i=0)+1e3).join('i+++" "+')+'i')

I also learned that running .map and .forEach on an initialised undefined filled Array does nothing... at least in FireFox anyway

Array(1000).forEach(function(){ /* this code is never executed :( */ })

Answer 11

Javascript, 71. No if, for, or recursive function

function f(i,c,b){a=[]
eval(s=b+";a[++i]=s;a=a.slice(0,c);eval(a[i])")}

Test:

f(0,1000,'console.log(i)')

Answer 12

Spaghetti PHP 44

<?$i=0;a:if($i<1001){echo $i++." ";goto a;}

Answer 13

Python 2.7, 60 Bytes with command-line parameter

Prints 'O' to the console:

import sys
def l(t,m):
 print 'O'
  if t!=m:
   l(t+1,m)
l(0,int(sys.argv[0]))

EDIT: Realised it didn't work, so byte count has gone up to fix On another note, here's a 127 byte version, including print function, that will let you actually call functions with one argument

import sys
def println(a):
print(a)
def l(t,m,f,a): 
    f(a) 
    if t!=m:
        l(t+1,m,f,a)
p=println
l(0,int(sys.argv[1]),p,"there")

Answer 14

Objective-C 58 Characters (Or 45...)

int i;
-(void)f {
    NSLog(@"%d",i++);
    if (i<1000) [self f];
}

[self f];

*13 chars went on printing i, so only the for-loop is actually 45...

Answer 15

sh

cat -An /dev/urandom|head -n1000|cut -f1|xargs

Answer 16

Python 2.x - 17 chars

print range(1000)

Answer 17

Language = C

just loop - 59 characters

(int(*)())\x66\x31\xc0\x66\x40\x66\x3d\xe8\x03\x75\xf8\xc3"

loop+call - 92 characters

(int(*)())"\x66\x31\xc0\x8b\x5c\x24\x04\x66\x40\x50\xff\xd3\x58\x66\x3d\xe8\x03\x75\xf4\xc3"

Example usage:

#include <stdio.h>

void disp(int n){printf("%d ", n&(0xffff));}

int main(){
    ((int(*)())"\x66\x31\xc0\x8b\x5c\x24\x04\x66\x40\x50\xff\xd3\x58\x66\x3d\xe8\x03\x75\xf4\xc3")(&disp);
    return 0;
}

This will only work on x86 machines. Tested with gcc (and works on codepad.org -> http://codepad.org/uyhFR9XU)

int fn(int n){ // n is at esp+4

    xor %ax, %ax ; zeros ax
    mov 4(%esp), %ebx ; saves esp+4 (addr of n) to ebx

    body:
    inc %ax ; add one to ax (this will print from 1 to 1000 instead of 0-999)
    push %eax ; pushes eax onto the stack
    call *%ebx ; calls n, which should contain &disp
    pop %eax ; pop eax off the stack assuming disp did not use eax
    cmp $1000, %ax ; compare
    jne body ; if not 1000, goto body

    ret
}

Answer 18

Scala:

(1 to 100)mkString" "

21 chars not that ugly:

(1 to 100) mkString " "

Answer 19

APL (26)

{(⊃⍵)>⊃⌽⍵:⍬⋄⍺⍺∇⍵+1 0⊣⍺⍺⊃⍵}

Usage:

<function> {(⊃⍵)>⊃⌽⍵:⍬⋄⍺⍺∇⍵+1 0⊣⍺⍺⊃⍵} <start> <end>

i.e.

{⍞←⍵ ' '} {(⊃⍵)>⊃⌽⍵:⍬⋄⍺⍺∇⍵+1 0⊣⍺⍺⊃⍵} 1 100

prints the numbers from 1 to 100.

Answer 20

VB11 (95c)

Dim F As Action(Of Integer, Integer, Action(Of Integer)) =
  Sub(i, m, a)
    If i > m Then Return
    a(i)
    F(i + 1, i, a)
  End Sub

And in use

 F(1, 1000, Sub(X) Console.WriteLine(X))

C# 52

f(int i,int m, action<int> a){if(i<=m){a(i);f(i-1,m,a);}

Answer 21

Python 2.6 (42)

def f(i,p,j=0):j<i and(p(j)or f(i,p,j+1))

# Test:
def do(i):
    print i
f(100,do)

This for-Function also includes the break command:

def do(i):
    print i
    if i==7:
        return True
        # break
f(100,do)

Answer 22

clang (152)

Tested with Apple clang version 4.0

bfor(int n,void(^b)(int)){
    __block void(^e)(int,int)=^(int l,int h){
        int m;
        h<l?:(m=(l+h)/2,e(l,m-1),b(m),e(m+1,h));
    };
    e(0,n-1);
}

Usage:

main(){
    bfor(100,^(int i){
        printf("%d ", i);
    });
    puts("");
}

The stack depth is log2 of the count due to the binary tree and thus it's unlikely to overflow due to recursion.

Answer 23

Ti-84 Basic, 34

Here, > represents the calculator's STO-> button.

:-1>I:Lbl A:I+1>I:If I<1000:Goto A

Answer 24

Golf-Basic 84, 23 characters

:-1_Il`A:I++I@I<1000o`A

Answer 25

Lua, 59

local function f(x)if x<1000 then return f(x+1)end end f(0)

The loop body is located right after the then. This does not overflow stack because of the tail call optimization.

Test case:

local function f(x)if x<1000 then print(x)return f(x+1)end end f(0)

Answer 26

Same as @houbysoft, but in C++.

#include <iostream>
#include <vector>

int main(int argc, char *argv[])
{
    int i = 0;
    std::function<int()> m = [&i, &m]()->int {
        std::vector<std::function<int()>> functors;
        functors.push_back(m);
        functors.push_back([]()->int{return 0;});
        i++;
        std::cout << i << std::endl;
        functors[i>999]();
        return i;
    };
    m();
    return 0;
}

And Objective C (Just C using blocks, actually...)

#import <Foundation/Foundation.h>

int main(int argc, char *argv[])
{
    __block int i = 0;
    __block int (^m)();
    m = ^() {
        int (^a[])() = {m, ^(){return 0;}};
        i++;
        NSLog(@"i: %d", i);
        a[i>9]();
        return i;
    };
    m();
    return 0;
}

Answer 27

Nemerle (?c)

macro for (init, cond, change, body)
syntax ("for", "(", init, ";", cond, ";", change, ")", body)
{
 <[ 
   $init;
   def loop () : void
   {
     if ($cond) { $body; $change; loop() } 
        else ()
   };
   loop ()
  ]>
}

Usage

 for (mutable i = 0, i < 10, i++, printf ("%d", i))

Answer 28

Lua (63 chars)

function F(n,f,...)if n>0 then f(...)return F(n-1,f,...)end end

Slightly longer, but more generic, than @mniip's version. Use like F(1000,print,' ').

Answer 29

C - 48 characters

Compilable code.

main(int i){i^1002&&main(i+1);printf("%i",i-2);}

Answer 30

CPython 2, 158 bytes

(Yes, this is both implementation and version specific)

class K(object):
 def __init__(s,b,c,e,n):
  if not n:n={};exec b in n
  else:exec e in n
  s.n=n;s.c=c;s.e=e
 def __del__(s):eval(s.c,s.n)or K(0,s.c,s.e,s.n)

Example usage:

K('i=55','i<88','i+=1;print i`,0)