🚀 go-pugleaf

In <comp.std.c++> maxtal@extro.ucc.su.OZ.AU (John MAX Skaller) writes:
>	You could always write the progam in terms of cmp(T,T),
>not <. The it would work for pointers too, you would just
>have to define cmp(T,T) for each type, including pointers,

I think that would be a serious effort, considering how many different
types of pointers you have in an application.

>	template<class T> int cmp(T a1, T a2){return a1<a2;}
>	int cmp(void* a1, void* a2){return ptrcmp(a1,a2)<0;}

I don't think this one flies.  For example,

	int* p;
	int* q;
	cmp(p, q);

probably causes a template overloading ambiguity.  You have to
explicitly define a cmp() for every type of pointer you have, I think.

>	The real problem cannot be solved at all, namely, for
>a user define < or cmp, ensuring it is a total order.

That is true, of course, for many applications.

I would also like to point out a few errors in the code for class Tree
in an earlier posting.  The specializations for void* in a few places
says "const void*&" which should be "void* const&".  Another error is
that Insert() returns a T&, which should be a const T&.

The first error I made, and the fact that nobody found it, is a strong
indication that specialization of templates is a real complication.


				-- Dag