• Xinok (6/6) Jan 09 2007 Is it possible to create template parameters in the D language?
• Don Clugston (12/19) Jan 09 2007 Too complicated, and not powerful enough!
• Xinok (19/33) Jan 09 2007 I see template parameters as a 'self documenting' feature, so the develo...

Xinok <xnknet gmail.com> writes:

Is it possible to create template parameters in the D language?
template <template <class T> class T> class N;

I think this would be the most obvious syntax, but it doesn't seem to work:
template temp(template T(T1)){ }


My second question, is it possible to specialize by template arguments?
template temp(T : T!(T1 : int))

Don Clugston <dac nospam.com.au> writes:

Xinok wrote:
 Is it possible to create template parameters in the D language?
 template <template <class T> class T> class N;
 
 I think this would be the most obvious syntax, but it doesn't seem to work:
 template temp(template T(T1)){ }

Too complicated, and not powerful enough!

template temp(alias T) {
    T!(T1);
}

alias parameters are a generalisation of template template parameters.
T1 doesn't have to be a template, just anything that has a name.

 My second question, is it possible to specialize by template arguments?
 template temp(T : T!(T1 : int))

Yes.

template temp(alias T1: T!(int) )
{
}

And you can have default alias template arguments, too.

Xinok <xnknet gmail.com> writes:

Don Clugston Wrote:

 template temp(alias T) {
     T!(T1);
 }
 
 alias parameters are a generalisation of template template parameters.
 T1 doesn't have to be a template, just anything that has a name.

I see template parameters as a 'self documenting' feature, so the developer
knows two things:
1) The template is looking for a template
2) The dev knows what arguments the template needs

If you apply a template to an alias, you can basically make any template
compatible with the template argument:

template a(int V, T){ }

template b(template T(T, int V)){ }

template al(T, int V){
	alias a!(V, T) al;
}

b!(al) // Makes template 'b' compatible with template 'a'

And regardless if you use an alias or template argument, you'd still have to
define template 'al'.


 Yes.
 
 template temp(alias T1: T!(int) )
 {
 }
 
 And you can have default alias template arguments, too.
 

I tried the following code:
template temp(alias T){
}

template temp(alias T : T!(int)){
}

And got the error:
template main.temp(alias T : T!(int)) conflicts with main.temp(alias T) at
main.d(4)