AliasSeq of AliasSeq, or meta-functions that take multiple lists

[Ali Çehreli via Digitalmars-d-learn]

On 06/19/2017 12:54 PM, Jean-Louis Leroy wrote:
> I need to process two sequences in parallel (select some elements of
> sequence A depending of the corresponding element of sequence B). How
> can I pass two sequences to a meta-function? I tried nesting AliasSeqs
> but I get Perl4 style flattening:
>
>   AliasSeq!(AliasSeq!(int, float),
>             AliasSeq!(char, double))
>   -> (int,float,char,double)
>
> I worked around the problem by passing a single AliasSeq to my
> meta-function and using indexation to access the two sub-lists but now I
> need to process three sequences in parallel and I am looking for a
> cleaner solution.
>
>

Hi Jean-Louis! :)

One option is to nest templates:

template foo(Args1...) {
     void bar(Args2...)() {
     }
}

void main() {
     foo!(int, float).bar!(char, double)();
}

Ali