Re: foreach

[Rikki Cattermole via Digitalmars-d]

On 13/06/2014 3:00 a.m., Manu via Digitalmars-d wrote:

I often find myself wanting to write this:
   foreach(; 0..n) {}
In the case that I just want to do something n times and I don't
actually care about the loop counter, but this doesn't compile.

You can do this:
   for(;;) {}

If 'for' lets you omit any of the loop terms, surely it makes sense
that foreach would allow you to omit the first term as well?
I see no need to declare a superfluous loop counter when it is unused.

Of course my reaction is a library solution:

import std.stdio;
import std.traits;

void times(size_t n, void delegate() c) {
        for (size_t i = 0; i < n; i++)
                c();
}

void times(size_t n, void delegate(size_t) c) {
        for (size_t i = 0; i < n; i++)
                c(i);
}

void iterate(T, U = typeof((T.init)[0]))(T t, void delegate(U) c) {
        foreach(v; t)
                c(v);
}

void iterate(T, U = typeof((T.init)[0]))(T t, void delegate(U, size_t) c) {
        foreach(i, v; t)
                c(v, i);
}

void main() {
        4.times({
                writeln("hi");
        });
        
        4.times((i) {
                writeln("hello ", i);
        });
        
        [1, 2, 3].iterate((uint c) {
                writeln("letter: ", c);
        });
        
        [1, 2, 3].iterate((uint c, i) {
                writeln("letter: ", c, ", at: ", i);
        });
}

But not really what you're wanting I'd imagine.