• David Medlock <amedlock nospam.org> Dec 09 2004
• "Ben Hinkle" <bhinkle mathworks.com> Dec 09 2004
• David Medlock <amedlock nospam.org> Dec 09 2004

David Medlock <amedlock nospam.org> writes:

I think its been brought up before that since mixins do not override a 
function declaration in its scope with a function in the template of the 
same name, you cannot use mixins for copying useful functions for 
similar types.

in C++ you can use

template<class T>T max( T a, T b )
{
   if ( a < b ) return b; else return a;
}

In D the way would be:

template Algo(T)
{
   T max( T a, T b ) { if ( a < b ) return b; else return a; }
}

mixin Algo!(float);
mixin Algo!(int);
...

This does not seem to work since mixins are not aware of different 
function signatures, they seem to just look at names.

I don't see an easy way to accomplish this in D, unless I am missing 
something.

IMO this is a mistake not to add before 1.0 to make D competitive with C++.

"Ben Hinkle" <bhinkle mathworks.com> writes:

 template Algo(T)
 {
    T max( T a, T b ) { if ( a < b ) return b; else return a; }
 }

 mixin Algo!(float);
 mixin Algo!(int);


To overload use alias:
 mixin Algo!(float);
 mixin Algo!(int);
 alias Algo!(float).max max;
 alias Algo!(int).max max;

Or if you substitute "max" for "Algo" it looks a little nicer:
template max(T)
{
   T max( T a, T b ) { if ( a < b ) return b; else return a; }
}
class Foo {
 // don't even need to mix in
 alias .max!(float) max;
 alias .max!(int) max;
}
int main() {
 Foo x = new Foo;
 x.max(10,10);
 x.max(1.0,3.4);
 return 0;
}

Then again I'm not sure why you are mixing in a max template since just
leaving it in the global scope seems simpler:
template max(T)
{
   T max( T a, T b ) { if ( a < b ) return b; else return a; }
}
int main() {
 max!(int)(10,10);
 max!(float)(1.0,3.4);
 return 0;
}
but then you are probably just making up this example to simplify the
posting, no?

-Ben

David Medlock <amedlock nospam.org> writes:

Ben Hinkle wrote:
template Algo(T)
{
   T max( T a, T b ) { if ( a < b ) return b; else return a; }
}

mixin Algo!(float);
mixin Algo!(int);


 
 To overload use alias:
  mixin Algo!(float);
  mixin Algo!(int);
  alias Algo!(float).max max;
  alias Algo!(int).max max;
 


Thanks for the heads up on the alias, I will try it.


 Then again I'm not sure why you are mixing in a max template since just
 leaving it in the global scope seems simpler:
 template max(T)
 {
    T max( T a, T b ) { if ( a < b ) return b; else return a; }
 }
 int main() {
  max!(int)(10,10);
  max!(float)(1.0,3.4);
  return 0;
 }
 but then you are probably just making up this example to simplify the
 posting, no?
 
 -Ben
 


Yes the example is a bit simpler.  I am doing a 3d Math package centered 
around OpenGL which needs 2,3,4 size Vectors of different types(mostly 
just int and float).

I was trying to get top level functions like dot( a, b ) which seem more 
natural to me than a.dot(b), not to mention they match the OpenGL 
shading language built in functions.

It still seems a little strange the mixin looks at the name rather than 
the type signature, though.

Tbanks again for the help.
-David