Hello,

I need to do something like this :

/* ---- CODE ---- */
import tango.io.Stdout;


interface I
{
  bool cmpType(U)(U val);
}

class  A(T):I
{
  bool cmpType(U)(U val)
  {
    static if ( is (U==T) )
      return true;
    else
      return false;
  }
}

void main()
{
  I a = new A!(int);

  int tInt = 10;
  double tDouble = 20;
  float tFloat = 30;
  a.cmpType(tInt);
  a.cmpType(tDouble);
  a.cmpType(tFloat);
}
/* ---END CODE ---- */

But it's not allow by the compiler when there's no problem when change the line:
  I a = new A!(int);
By
  A a = new A!(int);

:-(

Does something have an idea on how to do something like this ?

Thanks in advance,
Tsalm

TSalm wrote:
> Does something have an idea on how to do something like this ?

You don't. Templates cannot participate in polymorphism. I've dealt with this in the past and ended up making another class with a template parameter that corresponds to the desired function template parameter...

Basically, you change:

interface IFoo
{
	void method(T)(T t);
}

to:
interface IFoo(T)
{
	void method(T t);
}

This only works in some situations.


> Thanks in advance,
> Tsalm

Le Sun, 01 Mar 2009 03:07:16 +0100, Christopher Wright <dhasenan@gmail.com> a écrit:

> TSalm wrote:
>> Does something have an idea on how to do something like this ?
>
> You don't. Templates cannot participate in polymorphism. I've dealt with this in the past and ended up making another class with a template parameter that corresponds to the desired function template parameter...
>
> Basically, you change:
>
> interface IFoo
> {
> 	void method(T)(T t);
> }
>
> to:
> interface IFoo(T)
> {
> 	void method(T t);
> }
>
> This only works in some situations.
>
But, in fact, I need to call a "template-method" of a "template-class", for which the calling code doesn't know the type of the "template-class" to call this method.
It's why I tried to use an Interface.

TSalm wrote:
> Le Sun, 01 Mar 2009 03:07:16 +0100, Christopher Wright <dhasenan@gmail.com> a écrit:
> 
>> TSalm wrote:
>>> Does something have an idea on how to do something like this ?
>>
>> You don't. Templates cannot participate in polymorphism. I've dealt with this in the past and ended up making another class with a template parameter that corresponds to the desired function template parameter...
>>
>> Basically, you change:
>>
>> interface IFoo
>> {
>>     void method(T)(T t);
>> }
>>
>> to:
>> interface IFoo(T)
>> {
>>     void method(T t);
>> }
>>
>> This only works in some situations.
>>
> But, in fact, I need to call a "template-method" of a "template-class", for which the calling code doesn't know the type of the "template-class" to call this method.
> It's why I tried to use an Interface.

The remaining way:
void methodThatUsesTemplateOnAClass(Class)(Class instance)
{
	instance.method!(SomeArgument)();
}

You just can't store these arguments easily.