How to use interface template? How to model interface template properly in D.

[Jonathan M Davis]

On 2011-05-26 23:48, Matthew Ong wrote:
> On 5/27/2011 2:32 PM, Jacob Carlborg wrote:
> > On 2011-05-27 07:55, Matthew Ong wrote:
> > 
> > 
> > In D the syntax for declaring a template and instantiate a template is
> > not the same. Have a look at the first example of
> > http://www.digitalmars.com/d/2.0/template.htm
> > If don't understand after reading that example please ask again, I don't
> > want to just give away the answer. You'll learn more by reading the
> > documentation and figuring it out by yourself.
> 
> Hi Jacob,
> 
>  > In D the syntax for declaring a template and instantiate a template
> 
> is  not the same.
> I do understand that declaring is with () and instantiate is !().
> That is the reason that I am asking
> // ### or IS IT: DefType1!(T1) ??
> RetVal1(T1) obj = new RetVal1(T1)(); // ### or IS IT: new RetVal1!(T1)();
> 
> I read that document. There are little but no practical model.
> 
> Is there any such syntax being used within the probos lib?

struct S(T)
{
    this(T val)
    {
        this.val = val;
    }

    T val;
}

auto s = S!(int)(42);

or if S were a class

auto s = new S!(int)(42);

The parens are optional when there's only one template argument, so it could 
be S!int(42) and new S!int(42) instead.

There is no ! in the template definition, but you always use it when 
instantiating, unless it's inferred (which can be done with functions but not 
types). e.g.

T func(T)(T val)
{
    return val + 2;
}

auto v = func!int(5);
auto w = func(5);
assert(v == w);

- Jonathan M Davis