RE: [GD-General] Re: Simulating constrained genericity in C++

[Brian H. <bri...@py...>]

>This approach is fundamentally wrong: unlike Eiffel C++ doesn't use 
>classes to model attributes like being assignable or addable.

So what does C++ use?  Anything at all?  Near as I can tell, from my
ages old usage of templates, C++ is like a static version of Obj-C -- if
the function call/operator overload doesn't exist that you need, you get
a compile time warning (in Obj-C you can still send a message that isn't
understood, which is unbelievably powerful).

>of this templates work more like objects in a dynamic language and 
>rely on name commonality.

Right.  And I'm not sure if relying on name commonality is really a good
design decision.  For example, some STL classes require operator < to be
overloaded, which goes back to a thread on another mailing list where I
said that function name overloading is a Bad Idea so long as you're
using text as your representation because you can't find, for example,
every place you're doing a comparison between two specific types.

There are reasonable reasons for saying:

Foo a, b;

if ( a < b )
   return true;

is prettier than:

Foo a, b;

if ( a.compareToFoo( b ) < 0 )
   return true;

But at least when I need to know where I'm comparing Foos I can find it
immediately with grep.

But that's neither here nor there =)

>Eiffel reminds me of Modula-2: a really nice implementation of 
>yesterdays paradigm. But it just doesn't offer enough over C++ to be 
>compelling (for me at least).

I don't know if Eiffel's implementation of constrained genericity is
yesterday's paradigm; it's just a different way of doing things.  Eiffel
still has significant other problems, but I think its support of
constrained genericity looks pretty elegant (at least, on paper).

For me, the incremental advantages over C/C++ are probably to be found
in Obj-C and Java.  The former provides fully dynamic typing/message
passing; the latter provides garbage collection and a shit load of stock
libraries and cross-platform compatibility.

Brian