Create constraint for each parameter in template arg pack

[vit]

On Tuesday, 28 August 2018 at 12:28:19 UTC, Andrey wrote:
> Hello,
> Let we have two variadic templates:
>> template Qwerty(Values...) {}
>> template Qaz(alias type, Data...) {}
>
> Now I want to add a constraint to "Qwerty" so that each type in 
> "Values" pack must be a "Qaz" template. I don't care about 
> values of "type" or "Data" in "Qaz".
> How to do it in D?


import std.meta : allSatisfy;

template Qwerty(Values...)
if(allSatisfy!(isQaz, Values)){

}
template Qaz(alias type, Data...) {}

enum isQaz(alias Q : Qaz!Args, Args...) = true;
enum isQaz(Args...) = false;

alias Foo = Qwerty!(Qaz!(i => i), Qaz!(i => i), Qaz!(i => i));