[LC++]Generic programming vs OO inheritance

[Kai Vehmanen]

On Thu, 16 Aug 2001, Mark Phillips wrote:

> You've almost convinced me on this point.  Template "typename" (or
> "class") parameters give no information about the type of class which
> may be passed in.  This is in contrast to the OO base-class approach
> where the base-class effectively defines the type of class that
> pointers to this base-class are allowed to represent.  This is why I

I've always liked Eiffel's template system. Basicly it ties OO and generic
programming closely together. Here's a short code example:

--cut--
class SUM[T -> NUMERIC]
inherit
	COMBINE[T]
feature
	[class definition]
--cut--

Ie. class SUM has a generic parameter T, which must be derived from the
NUMERIC base class (interface class). SUM[T] then inherits from another
generic class COMBINE[T].

The same thing happens in C++, but in Eiffel the required interface is
explicitly stated. And this is a very nice feature. For instance all
algorithms working on collections can be templatized with T->COLLECTION,
etc...

My biggest grief with gcc C++ templates is the lack of support for export.
As it is now, I have to include the routine implementations from header
files. In a big project, with widely used template classes, this means
that a small change to the implementation of some template class routine
implementation results in recompilation of practically the whole system.
This is extremely inconvenient.

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