• bearophile (19/19) Jan 28 2014 In std.typecons there is this template, that tells if a given
• Jakob Ovrum (16/35) Jan 28 2014 We can already do this, but you have to omit the `Unused` alias
• Andrej Mitrovic (2/5) Jan 29 2014 Me too, but I can't remember if this was filed in bugzilla.
• bearophile (4/10) Jan 29 2014 Thank you.

"bearophile" <bearophileHUGS lycos.com> writes:

In std.typecons there is this template, that tells if a given 
type is any tuple, this means if it's the instantiation of a 
Tuple with any argument type:


template isTuple(T)
{
     static if (is(Unqual!T Unused : Tuple!Specs, Specs...))
     {
         enum isTuple = true;
     }
     else
     {
         enum isTuple = false;
     }
}


Do you think it's worth a D enhancement request to be able to 
write that code like this?

enum isTuple(T) = is(Unqual!T Unused : Tuple!Specs, Specs...);

Bye,
bearophile

"Jakob Ovrum" <jakobovrum gmail.com> writes:

On Wednesday, 29 January 2014 at 02:30:00 UTC, bearophile wrote:
 In std.typecons there is this template, that tells if a given 
 type is any tuple, this means if it's the instantiation of a 
 Tuple with any argument type:


 template isTuple(T)
 {
     static if (is(Unqual!T Unused : Tuple!Specs, Specs...))
     {
         enum isTuple = true;
     }
     else
     {
         enum isTuple = false;
     }
 }


 Do you think it's worth a D enhancement request to be able to 
 write that code like this?

 enum isTuple(T) = is(Unqual!T Unused : Tuple!Specs, Specs...);

 Bye,
 bearophile

We can already do this, but you have to omit the `Unused` alias 
(a semi-recent enhancement allows for that):

---
import std.traits : Unqual;

struct Tuple(Args...) {}

enum isTuple(T) = is(Unqual!T : Tuple!Types, Types...);

void main()
{
	Tuple!(int, string) t;
	static assert(isTuple!(typeof(t)));
}
---

On a related note, I would like the body of a template to be able 
to access aliases introduced in IsExpression's in the template's 
constraints.

Andrej Mitrovic <andrej.mitrovich gmail.com> writes:

On 1/29/14, Jakob Ovrum <jakobovrum gmail.com> wrote:
 On a related note, I would like the body of a template to be able
 to access aliases introduced in IsExpression's in the template's
 constraints.

Me too, but I can't remember if this was filed in bugzilla.

"bearophile" <bearophileHUGS lycos.com> writes:

Jakob Ovrum:

 We can already do this, but you have to omit the `Unused` alias 
 (a semi-recent enhancement allows for that):

 ---
 import std.traits : Unqual;

 struct Tuple(Args...) {}

 enum isTuple(T) = is(Unqual!T : Tuple!Types, Types...);

Thank you.

Bye,
bearophile