• Matthew Dudley (37/37) Jan 31 2014 So this is the general form of what I'm trying to do:
• bearophile (22/24) Jan 31 2014 You have to remember that an instantiated template creates a

"Matthew Dudley" <pontifechs gmail.com> writes:

So this is the general form of what I'm trying to do:


import std.stdio;

class Foo(uint something)
{
   Foo opBinary(string op)(Foo rhs) const
     if (op == "*")
   {
     writeln("calling Foo.*");
   }
}

class Bar : Foo!(3)
{
   // ...
}

class Baz : Foo!(4)
{
   //...
}

void main()
{
   auto bar = new Bar();
   auto baz = new Baz();

   auto foo = bar * baz;
   // errors with
   // tinker.d(28): Error: 'cast(Object)bar' is not of arithmetic 
type, it is a object.Object
   // tinker.d(28): Error: 'baz' is not of arithmetic type, it is 
a tinker.Baz
}


I'm still fairly new to D, and my google-fu has failed me. I 
don't understand this error. If I remove the templating from all 
3 classes, it compiles just fine, and does what I would expect.

It feels like the compiler is maybe ignoring Foo.opBinary? Does 
the compiler not consider Foo!4 to be a valid argument for 
Foo.opBinary? If that's the case, is there a way to tell the 
compiler that Foo.opBinary should accept all specializations for 
a parameter?

"bearophile" <bearophileHUGS lycos.com> writes:

Matthew Dudley:

 I'm still fairly new to D, and my google-fu has failed me. I 
 don't understand this error.

You have to remember that an instantiated template creates a 
totally distinct type.

There are few different ways to face your problem, this is one of 
them:


import std.stdio;

class Foo(uint N) {
     Foo opBinary(string op, uint N2)(Foo!N2 rhs) const
     if (op == "*") {
         "calling Foo.*".writeln;
         return new Foo;
     }
}

class Bar: Foo!3 {}
class Baz: Foo!4 {}

void main() {
     auto bar = new Bar;
     auto baz = new Baz;
     auto foo = bar * baz;
}


Bye,
bearophile