• TSalm <TSalm free.fr> Feb 28 2009
• Christopher Wright <dhasenan gmail.com> Feb 28 2009
• TSalm <TSalm free.fr> Mar 01 2009
• Christopher Wright <dhasenan gmail.com> Mar 01 2009

TSalm <TSalm free.fr> writes:

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

Christopher Wright <dhasenan gmail.com> writes:

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

TSalm <TSalm free.fr> writes:

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.


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.

Christopher Wright <dhasenan gmail.com> writes:

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.


 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.