Another foreach idea.

[zadok]

Kirk McDonald wrote:
> Kirk McDonald wrote:
>> In short, all you need is a "range" function that returns an array of 
>> integers, or (alternately) a generator... something like this:
>>
> 
> Oh! I did some thinking and improved it a little. It's a struct now, so 
> it doesn't need to touch the GC. And factory functions are maybe a 
> little more clear than static opCalls (also, there are two, now).
> 
> private import std.stdio;
> 
> struct range_struct {
> public:
>     int m_start, m_end, m_step;
> 
>     // Compares whether i has reached the end
>     private bool cmp(int i) {
>         if (m_step > 0 && i < m_end) return true;
>         else if (m_step < 0 && i > m_end) return true;
>         else return false;
>     }
> 
>     int opApply(int delegate(inout int) dg) {
>         int result = 0;
>         for (int i=m_start; this.cmp(i); i+=m_step) {
>             result = dg(i);
>             if (result) break;
>         }
>         return result;
>     }
> }
> 
> range_struct range(int start, int end, int step=1) {
>     range_struct r;
>     r.m_start = start;
>     r.m_end   = end;
>     r.m_step  = step;
>     return r;
> }
> 
> range_struct range(int end) {
>     return range(0, end, 1);
> }
> 
> void main() {
>     foreach(i; range(10)) {
>         writefln("%s", i);
>     }
>     foreach(j; range(10, 20)) {
>         writefln("%s", j);
>     }
>     foreach(k; range(0, 10, 2)) {
>         writefln("%s", k);
>     }
> }
> 
> -Kirk McDonald

make your struct predefined in the language with the syntaxic sugar 
start..end
and this would be fine to compile:

range r = 0..9;
assert(r == range(0, 9));

r = range(0, 9, 2);
char[] str = "0123456789";
assert(str[r] == "02468");