Newish to D, so bare with me~

I have a few questions surrounding Class Templates and the like if anyone has time.

After reading the two pages on templates (lex, and revisited) I haven't seen anything regarding interfaces being templated like classes. However it doesn't produce a lexical error :

public interface H(T){
   T another();
}
public class A(T) : H!(T)
{
   T t;
   T another(){return t;}
   void curious(){}
}

What I'm aiming for is an equivalent to c#'s generic interfaces. So I can remove casting on my interface declarations.
However, when I do this :
 alias A!(int) a;
 assert(a.another()==0);

I get the following error : Error: need 'this' to access member another.

So, is there a way where I can template interfaces as I do classes to give a per type based interfaces to the classes?

Further on...

How do I get the A class instantiated? Is that possible with templated classes?

public class A(T)
{
	T t;
   	this(){}
}

 alias A!(int) a;
 a b = new a(); // doesn't work
 A! b = new A!(int)();// doesnt either?

 Am I wrong to think that I can use and approach class templates as if I were using generics in c#?
 Or am I going about it the wrong way?

Running out the door: this works for me with D 1.0:


interface H(T)
{
    T another();
}

class A(T) : H!(T)
{
    T t;
    T another() { return t; }
    void curious() { }
}

import std.stdio;

void main()
{
    alias A!(int) a;
    a b = new a;
    A!(int) c = new A!(int);
    H!(int) d = new A!(int);

    writefln("b.another: ", b.another);
    writefln("c.another: ", c.another);
    writefln("d.another: ", d.another);
}


	-- Daniel

Robby schrieb am 2007-01-15:
> Newish to D, so bare with me~
>
> I have a few questions surrounding Class Templates and the like if anyone has time.
>
> After reading the two pages on templates (lex, and revisited) I haven't seen anything regarding interfaces being templated like classes. However it doesn't produce a lexical error :
>
> public interface H(T){
>     T another();
> }
> public class A(T) : H!(T)
> {
>     T t;
>     T another(){return t;}
>     void curious(){}
> }
>
> What I'm aiming for is an equivalent to c#'s generic interfaces. So I
> can remove casting on my interface declarations.
> However, when I do this :
>   alias A!(int) a;
>   assert(a.another()==0);
>
> I get the following error : Error: need 'this' to access member another.

"a" is a type, not an instance:

# alias A!(int) a;
#
# int main(){
#    a b = new a();
#    assert(b.another() == 0);
#    return 0;
# }

> So, is there a way where I can template interfaces as I do classes to give a per type based interfaces to the classes?
>
> Further on...
>
> How do I get the A class instantiated? Is that possible with templated classes?
>
> public class A(T)
> {
> 	T t;
>     	this(){}
> }
>
>   alias A!(int) a;
>   a b = new a(); // doesn't work
>   A! b = new A!(int)();// doesnt either?

If the above code is at module level it will fail due to "new ..." being a non-constant expression:

# alias A!(int) a;
# a b;
# A!(int) c;
#
# static this(){
#    b = new a();
#    c = new A!(int)();
# }

Thomas

You almost had it right, but made a couple of minor coding mistakes.

> public interface H(T){
>    T another();
> }
> public class A(T) : H!(T)
> {
>    T t;
>    T another(){return t;}
>    void curious(){}
> }
> 
>  alias A!(int) a;
>  assert(a.another()==0);

In this code, "a" is a type not an object. I changed it to:
  alias A!(int) a;
  a aObject = new a;
  assert(aObject.another()==0);

> public class A(T)
> {
>     T t;
>        this(){}
> }
> 
>  alias A!(int) a;
>  a b = new a(); // doesn't work
>  A! b = new A!(int)();// doesnt either?

The last line is incorrect. I changed it to:
  A!(int) b2 = new A!(int)();

Hope that helps.

  Bradley

Sweet!, now I can port my collection classes to d without casting hell, thanks!

Robby

Bradley Smith wrote:
> You almost had it right, but made a couple of minor coding mistakes.
> 
>> public interface H(T){
>>    T another();
>> }
>> public class A(T) : H!(T)
>> {
>>    T t;
>>    T another(){return t;}
>>    void curious(){}
>> }
>>
>>  alias A!(int) a;
>>  assert(a.another()==0);
> 
> In this code, "a" is a type not an object. I changed it to:
>   alias A!(int) a;
>   a aObject = new a;
>   assert(aObject.another()==0);
> 
>> public class A(T)
>> {
>>     T t;
>>        this(){}
>> }
>>
>>  alias A!(int) a;
>>  a b = new a(); // doesn't work
>>  A! b = new A!(int)();// doesnt either?
> 
> The last line is incorrect. I changed it to:
>   A!(int) b2 = new A!(int)();
> 
> Hope that helps.
> 
>   Bradley