Re: Tree of pointers

From:

Obnoxious User <OU@127.0.0.1>

Newsgroups:

comp.lang.c++

Date:

29 Jun 2007 21:05:48 GMT

Message-ID:

<4685742c$0$9281$88260bb3@news.teranews.com>

On Fri, 29 Jun 2007 13:36:57 -0700, Travis wrote:

It's a tree that I wrote.

The tree is templated and can store anything of NODETYPE.

When I instantiate the tree, I make each node a pointer to my custom
class.

In my custom class I have == overloaded.

When I do a search for a node I provide it a NODETYPE to find.

It doesn't find it because even though the NODETYPE I provide as
search criteria is the same as a node in the tree, they aren't
occupying the same memory so the == operator never goes true. I have
to dereference int the NODETYPE and it works fine.

Perhaps the 'someone else' mentioned below actually wants that kind of
behaviour, ie address comparison.

My concern is the reusabilty of the tree. If someone else comes along
and makes NODETYPE some object (not a pointer), then the dereferencing
in my find routine will bomb right?

Can you elaborate a little more on how the STL handles this?

std::set<int*> m;

The default comparison for 'm' will also only compare addresses.
I need to provide my own comparison operator if I want something else.

struct s {
    bool operator()(int * a, int * b) {
        return a[5] < b[5];
    }
};
std::set<int*, s> ms;

--
                                 Obnoxious User