If I have a template parameter

    E = S!int

where

    struct S(T) { S x; }

how can I extract the template name part `S` from E`?

Something like:

    static assert(is(templateName!(S!int) == S));

Is this already in Phobos somewhere?

On Monday, 27 June 2016 at 16:40:09 UTC, Nordlöw wrote:
> If I have a template parameter
>
>     E = S!int
>
> where
>
>     struct S(T) { S x; }
>
> how can I extract the template name part `S` from E`?
>
> Something like:
>
>     static assert(is(templateName!(S!int) == S));
>
> Is this already in Phobos somewhere?

If I recall correctly, std.traits contains a TemplateOf trait, that should do exactly what you want.

On Monday, 27 June 2016 at 16:40:09 UTC, Nordlöw wrote:
> If I have a template parameter
>
>     E = S!int
>
> where
>
>     struct S(T) { S x; }
>
> how can I extract the template name part `S` from E`?
>
> Something like:
>
>     static assert(is(templateName!(S!int) == S));
>
> Is this already in Phobos somewhere?

import std.traits;
__traits(identifier, TemplateOf!(S!int));

On 06/27/2016 09:54 AM, Lodovico Giaretta wrote:
> On Monday, 27 June 2016 at 16:40:09 UTC, Nordlöw wrote:
>> If I have a template parameter
>>
>>     E = S!int
>>
>> where
>>
>>     struct S(T) { S x; }
>>
>> how can I extract the template name part `S` from E`?
>>
>> Something like:
>>
>>     static assert(is(templateName!(S!int) == S));
>>
>> Is this already in Phobos somewhere?
>
> If I recall correctly, std.traits contains a TemplateOf trait, that
> should do exactly what you want.

Yes, isIntanceOf:

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

Ali

On Monday, 27 June 2016 at 17:14:23 UTC, John wrote:
> On Monday, 27 June 2016 at 16:40:09 UTC, Nordlöw wrote:
>> If I have a template parameter
>>
>>     E = S!int
>>
>> where
>>
>>     struct S(T) { S x; }
>>
>> how can I extract the template name part `S` from E`?
>>
>> Something like:
>>
>>     static assert(is(templateName!(S!int) == S));
>>
>> Is this already in Phobos somewhere?
>
> import std.traits;
> __traits(identifier, TemplateOf!(S!int));

Scratch that, this is what you want:

import std.traits;
static assert(__traits(isSame, TemplateOf!(S!int), S));

On Monday, 27 June 2016 at 17:17:19 UTC, John wrote:
>> import std.traits;
>> __traits(identifier, TemplateOf!(S!int));
>
> Scratch that, this is what you want:
>
> import std.traits;
> static assert(__traits(isSame, TemplateOf!(S!int), S));

I believe this is what

    import std.traits : isInstanceOf;

is for.

Thanks! I found both useful.