d - How to create a tuple of ranges? -

template tupindextorange(alias tup, indicies...){   import std.meta;   import std.typecons;   static if(indicies.length == 0){     enum tupindextorange = tuple();   }   else{     enum tupindextorange = tuple(tup[ indicies[0] ][], tupindextorange!(tup,indicies[1..$]));   } }  void main(){   alias integrals = aliasseq!(array!int, array!float, array!double);   tuple!integrals integrals;   integrals[0].insertback(1);   integrals[1].insertback(2);   integrals[2].insertback(3);   auto t = tupindextorange!(integrals, 0, 1, 2);   auto r = zip(t.expand); } 

err:

source/app.d(119,34): error: variable integrals cannot read @ compile time source/app.d(119,33):        called here: tuple(integrals.__expand_field_2.opslice(), tuple()) source/app.d(119,56): error: template instance app.main.tupindextorange!(integrals, 2) error instantiating source/app.d(119,56):        instantiated here: tupindextorange!(integrals, 1, 2) source/app.d(219,12):        instantiated here: tupindextorange!(integrals, 0, 1, 2) 

i assume error appears because trying access range @ compile time? how tell d need access range @ run time?

this tupindextorange should do:

auto t = tuple(integrals[0][], integrals[1][], integrals[2][]); 

how tell d need access range @ run time?

by passing runtime parameter:

template tupindextorange(indicies...) {     auto tupindextorange(t)(t tup) {       static if(indicies.length == 0){         return tuple();       }       else{         return tuple(tup[ indicies[0] ][], .tupindextorange!(indicies[1..$])(tup).expand);       }     } } 

two things note:

1. the function nested in template allows specify indices , not type. if auto tupindextorange(t, indices)(t tup), woul have provide type explicitly.

2. we recurse calling .tupindextorange rather tupindextorange, want recurse via template in outer scope, not nested function.