Re: foreach multiple loop sugar

[TheHamster via Digitalmars-d-learn]

On Tuesday, 18 August 2015 at 15:51:55 UTC, ixid wrote:
Though sugar seems to be somewhat looked down upon I thought 
I'd suggest this- having seen the cartesianProduct function 
from std.algorithm in another thread I thought it would be an 
excellent piece of sugar in the language. It's not an earth 
shattering change but it makes something very common more 
elegant and reduces indentation significantly for multiple 
nested loops. Braces make nested loops very messy and any 
significant quantity of code in the loop body benefits from not 
being in a messy nesting.

import std.algorithm, std.range, std.stdio;


void main() {
        // Standard
        foreach(i; 0..10)
                foreach(j; 0..10)
                        foreach(k; 0..10)
                                writeln(i, j, k);
        
        // Better
        foreach(k, j, i; cartesianProduct(10.iota, 10.iota, 10.iota))
                writeln(i, j, k);
        
        
        // Sugar
        foreach(k, j, i; 0..10, 0..10, 0..10)
                writeln(i, j, k);

        //Following brace rules
        // Standard
        foreach(i; 0..10)
        {
                foreach(j; 0..10)
                {
                        foreach(k; 0..10)
                        {
                                writeln(i, j, k);
                        }
                }
        }
                
        // Sugar
        foreach(k, j, i; 0..10, 0..10, 0..10)
        {
                writeln(i, j, k);
        }


You can create a multi-loop quite easily in template form for 
avoid the nesting.

Essentially use an array for the the index instead of individual 
variables, e.g.,


mutliloop([0..10, 0..10, 0..10], (i)=>
{
   writeln(i[0], i[1], i[2]);
});


I'm not sure how efficient it is but essentially achieves what 
you are asking without too much overhead. Obviously having good 
language support is always nice...