I already read about "Implicit Template Properties":
If a template has exactly one member in it, and the name of that member is the same as the template name, that member is assumed to be referred to in a template instantiation

I guess the following is something similar, but why are aliases used here?

template ParameterTypeTuple(dg)
{
    static if (is(dg P == function))
	alias P ParameterTypeTuple;
    else static if (is(dg P == delegate))
	alias ParameterTypeTuple!(P) ParameterTypeTuple;
    else static if (is(dg P == P*))
	alias ParameterTypeTuple!(P) ParameterTypeTuple;
    else
	static assert(0, "argument has no parameters");
}

On Thu, Jan 22, 2009 at 10:56 AM, Trass3r <mrmocool@gmx.de> wrote:
> I already read about "Implicit Template Properties":
> If a template has exactly one member in it, and the name of that member is
> the same as the template name, that member is assumed to be referred to in a
> template instantiation
>
> I guess the following is something similar, but why are aliases used here?
>
> template ParameterTypeTuple(dg)
> {
>    static if (is(dg P == function))
>        alias P ParameterTypeTuple;
>    else static if (is(dg P == delegate))
>        alias ParameterTypeTuple!(P) ParameterTypeTuple;
>    else static if (is(dg P == P*))
>        alias ParameterTypeTuple!(P) ParameterTypeTuple;
>    else
>        static assert(0, "argument has no parameters");
> }
>

Aliases are members too.

Trass3r Wrote:

> I already read about "Implicit Template Properties":
> If a template has exactly one member in it, and the name of that member
> is the same as the template name, that member is assumed to be referred
> to in a template instantiation
> 
> I guess the following is something similar, but why are aliases used here?
> 
> template ParameterTypeTuple(dg)
> {
>      static if (is(dg P == function))
> 	alias P ParameterTypeTuple;
>      else static if (is(dg P == delegate))
> 	alias ParameterTypeTuple!(P) ParameterTypeTuple;
>      else static if (is(dg P == P*))
> 	alias ParameterTypeTuple!(P) ParameterTypeTuple;
>      else
> 	static assert(0, "argument has no parameters");
> }


Without the alias you will be declaring a variable.
With it you are aliasing a type.