• Lirong <leon.li.lirong gmail.com> Feb 17 2010
• Igor Lesik <curoles yahoo.com> Feb 18 2010
• "Lars T. Kyllingstad" <public kyllingen.NOSPAMnet> Feb 18 2010
• Lirong <leon.li.lirong gmail.com> Feb 18 2010

Lirong <leon.li.lirong gmail.com> writes:

Hi,

Can anyone show me how to detect if a symbol is template?

The following is not working:

template A()
{
...
}

alias a A;

static if(is (a == template)) // error

Best regards

Igor Lesik <curoles yahoo.com> writes:

Can anyone show me how to detect if a symbol is template?
The following is not working:
template A()
{
...
}
alias a A;
static if(is (a == template)) // error


imo, it is not possible; template name is not a type

in this particular case, to check if a is alias for A, you may use:
A.stringof == a.stringof

-Igor



----- Original Message ----
From: Lirong <leon.li.lirong gmail.com>
To: digitalmars-d puremagic.com
Sent: Wed, February 17, 2010 10:18:43 PM
Subject: detect if a symbol is template

Hi,

Can anyone show me how to detect if a symbol is template?

The following is not working:

template A()
{
...
}

alias a A;

static if(is (a == template)) // error

Best regards


      

"Lars T. Kyllingstad" <public kyllingen.NOSPAMnet> writes:

Lirong wrote:
 Hi,
 
 Can anyone show me how to detect if a symbol is template?
 
 The following is not working:
 
 template A()
 {
 ...
 }
 
 alias a A;
 
 static if(is (a == template)) // error
 
 Best regards


Is there any use case where it is useful to just know whether something 
is a template or not?

A template really can't be used for anything without instantiating it, 
and to instantiate it you need to know what parameters it takes. 
Checking whether a symbol is a template that takes a certain set of 
parameters is easy:

   template Foo() { ... }
   template Bar(T) { ... }

   static if (__traits(compiles, Foo!())) { ... }
   static if (__traits(compiles, Bar!int)) { ... }

-Lars

Lirong <leon.li.lirong gmail.com> writes:

Thank you!

This solves my problem.

I want to know a symbol is template so that I can use mixin with it.



Lars T. Kyllingstad Wrote:

 Lirong wrote:
 Hi,
 
 Can anyone show me how to detect if a symbol is template?
 
 The following is not working:
 
 template A()
 {
 ...
 }
 
 alias a A;
 
 static if(is (a == template)) // error
 
 Best regards


 Is there any use case where it is useful to just know whether something 
 is a template or not?
 
 A template really can't be used for anything without instantiating it, 
 and to instantiate it you need to know what parameters it takes. 
 Checking whether a symbol is a template that takes a certain set of 
 parameters is easy:
 
    template Foo() { ... }
    template Bar(T) { ... }
 
    static if (__traits(compiles, Foo!())) { ... }
    static if (__traits(compiles, Bar!int)) { ... }
 
 -Lars