Re: C++ not OOP? (Was: Language Efficiency

[ncohen@watson.ibm.com (Norman H. Cohen)]

In article <DAVIS.95Apr19112448@passy.ilog.fr>, davis@ilog.fr (Harley Davis)
writes: 

|> Start with an abstract interface to devices.  Write routines for all
|> shapes which use this abstract interface.  Then, for speed critical
|> shape/device pairs, write more specific multimethods which use
|> underlying device implementation information for optimization.
|> Indeed, I believe this is the textbook approach to using multimethods.

Yes, this is a far more compelling argument.

Of course this approach should only be used with one's eyes wide open
about the tradeoff between efficiency and maintainability: If the
implementation of a device is changed, it is no longer sufficient to
modify the method providing the standard interface.  You have to (1)
track down and (2) modify each of the specific multimethods.  (1) is the
hard part, since an interim solution for (2) is just to delete the
specialized multimethod and revert to the general method.

It should be noted that even in languages without direct linguistic
support for multiple dispatch, the same effect can be achieved in a
straightforward way by redispatching.

--
Norman H. Cohen    ncohen@watson.ibm.com