help on cartesianProduct()

[Orut via Digitalmars-d-learn]

On Sunday, 11 December 2016 at 23:07:16 UTC, Era Scarecrow wrote:
> On Sunday, 11 December 2016 at 18:05:19 UTC, Era Scarecrow 
> wrote:
>> On Sunday, 11 December 2016 at 16:34:38 UTC, Orut wrote:
>>> I need to be able to vary the number of ranges to feed into 
>>> cartesianProduct() at run time.
>>
>>  Hmmm... what kind of ranges? Are they going to be arrays? Or 
>> something else?
>
>
> Well, with the assumption of using arrays (since you kinda need 
> a length for it to work) I've thrown together a quick struct 
> that does the job. Not fully tested, but will do the same thing 
> with a varying number of inputs.
>
> [code]
> struct MultiCart(T) {
>     T[][] data;
>     int iteration;
>     int max;
>
>     this(T[][] _d, int iter=0) {
>         data = _d;
>         iteration = iter;
>
>         max = 1;
>         foreach(a; _d) {
>             if (a.length)
>                 max *= a.length;
>         }
>     }
>
>     T[] front() {
>         int i = iteration;
>         T[] val;
>
>         foreach(d; data) {
>             if (d.length) {
>                 val ~= d[i % d.length];
>                 i /= d.length;
>             }
>         }
>
>         return val;
>     }
>
>     void popFront() {
>         iteration++;
>     }
>
>     bool empty() {
>         return iteration >= max;
>     }
> }
>
> unittest {
>     import std.stdio;
>     alias CartInt = MultiCart!int;
>
>     int[] a=[1,2,3],b=[4,5],c=[6,7];
>     foreach(x; CartInt([a,b,c]))
>         writeln(x);
>
>     foreach(x; CartInt([a,b]))
>         writeln(x);
> }
> [/code]

The code works beautifully! Thank you very much. Will certainly 
acknowledge you as source of this code if this becomes of part of 
a bigger project. I hope others searching this forum would also 
discover this code.