[ANN] Multimethod.py -- multimethods for Python

[Gordon McMillan]

Doug Hellmann wrote:

> How is this different from function overloading, as implemented
> in C++? I'm not a C++  user, but my impression is the effect
> would be the same. Is that the point?

Not at all. C++ (and Java) are limited to figuring out one 
override / overload at a time. If you are dealing with base class 
pointers, you need to bounce the message around for awhile 
to resolve all of them. First, C++ will discover the proper 
derived class (the override), and then the proper overload. 
Unfortunately, this means declaring scads of methods which 
don't do anything except let the language stumble through the 
resolution.

So in order to do a nice simple case:
 widget->process(event)

You need to do something like:
  Widget::process(Event e) // not actually used
  Button::process(Event e) {e->getProcessedBy(this);}
  Text::process(Event e) {e->getProcessedBy(this);}

  SpewEvent::getProcessedBy(Button) ...
  BarfEvent::getProcessedBy(Text)...

but you also need to fill in most of the other squares of the 
cartesian product, or the language gets mad at you.
 
say-what-I-want-you-to-say-not-what-you-mean-ly y'rs

- Gordon