Replacing nested loops foreach using map/each/etc

[Alex Parrill via Digitalmars-d-learn]

On Monday, 25 May 2015 at 14:25:52 UTC, Dennis Ritchie wrote:
> Hi,
> Is it possible to write such a construction that could push 
> immediately to a conditional statement without using nested 
> loops? Ie organize search directly in the iterator if provided 
> by a map / each / iota and other support functions.
> Ie I want to write this code shorter :)
>
> import std.stdio;
>
> void main() {
>
>     const x = 12, y = 65, z = 50, s = 1435;
> 	
>     foreach (i; 0 .. x + 1)
>         foreach (j; 0 .. x + 1)
>             foreach (k; 0 .. x + 1)
>                 if (i * (y + 3 * z) + j * (y + 2 * z) + k * (y 
> + z) == s) {
>                     writeln(i + j + k);
>                     writeln(i * 3 + j * 2 + k);
>                     writeln(i * 3 + j * 2 + k);
>                     writeln(i, j, k);
>                 }
> }
> -----
> http://rextester.com/SJTU87854

Hint: Use `cartesianProduct` [1] with three iota ranges to 
replace the foreachs, and `filter` to replace the if

[1] 
http://dlang.org/phobos/std_algorithm_setops.html#.cartesianProduct