• Andrey (6/8) Aug 28 2018 Now I want to add a constraint to "Qwerty" so that each type in
• vit (9/17) Aug 28 2018 import std.meta : allSatisfy;
• bauss (14/22) Aug 28 2018 I'm not sure if there is a better way, but isInstanceOf
• Alex (3/27) Aug 28 2018 https://dlang.org/phobos/std_traits.html#TemplateOf
• Andrey (2/16) Aug 28 2018 Thank you everybody!
• vit (13/21) Aug 28 2018 Generic solution:

Andrey <saasecondbox yandex.ru> writes:

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?

vit <vit vit.vit> writes:

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));

bauss <jj_1337 live.dk> writes:

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?

I'm not sure if there is a better way, but isInstanceOf 
(std.traits) seems to work with a static foreach and a static if.

template Qwerty(Values...)
{
     static foreach (value; Values)
     {
         static if (!isInstanceOf!(Qaz, value))
         {
             static assert(0, "Values are not Qaz only ...");
         }
     }

     // ...
}

Alex <sascha.orlov gmail.com> writes:

On Tuesday, 28 August 2018 at 13:05:15 UTC, bauss wrote:
 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?

 I'm not sure if there is a better way, but isInstanceOf 
 (std.traits) seems to work with a static foreach and a static 
 if.

 template Qwerty(Values...)
 {
     static foreach (value; Values)
     {
         static if (!isInstanceOf!(Qaz, value))
         {
             static assert(0, "Values are not Qaz only ...");
         }
     }

     // ...
 }

https://dlang.org/phobos/std_traits.html#TemplateOf

maybe...

Andrey <saasecondbox yandex.ru> writes:

On Tuesday, 28 August 2018 at 13:05:15 UTC, bauss wrote:
 I'm not sure if there is a better way, but isInstanceOf 
 (std.traits) seems to work with a static foreach and a static 
 if.

 template Qwerty(Values...)
 {
     static foreach (value; Values)
     {
         static if (!isInstanceOf!(Qaz, value))
         {
             static assert(0, "Values are not Qaz only ...");
         }
     }

     // ...
 }

Thank you everybody!

vit <vit vit.vit> writes:

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?

Generic solution:


template Qwerty(Values...)
if(allSatisfy!(isInstanceOf!Qaz, Values)){

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



import std.meta : allSatisfy;
public import std.traits : isInstanceOf;
template isInstanceOf(alias T){
     import std.traits : impl = isInstanceOf;
     static enum isInstanceOf(alias X) = impl!(T, X);
     static enum isInstanceOf(X) = impl!(T, X);
}