Re: [boost] Weak_ptr and operator==

From: Joe Gottman (jgottman_at_[hidden])
Date: 2005-11-15 18:32:48

"Ben Artin" <macdev_at_[hidden]> wrote in message 
news:macdev-D3DEAB.17184015112005_at_sea.gmane.org...
> In article <f0e60a710511151400y3f557860ubf234ae67c83225_at_[hidden]>,
> Dan Day <coolmandan_at_[hidden]> wrote:
>
>> Why was operator== never added to weak_ptr? Couldn't the operator easily 
>> be
>> implemented in terms of operator<?
>
> <http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2004/n1590.html>
>

   Now that unordered_set and company have been added to tr1, we might want 
to consider how to keep weak_ptr's in them.  A major advantage of the 
ordered associative containers over their hash-based counterparts is the 
ability to do order-based searches, for example given a set<string> to find 
all elements that come before the string "dog".  This advantage doesn't 
really apply to weak_ptr's (or shared_ptr's for that matter) so given a 
choice between the a set<weak_ptr<string> > and an 
unordered_set<weak_ptr<string> > I think many users would chose the later if 
it were available.  To make it available we need two things: a hash function 
and an operator== on weak_ptrs.

Joe Gottman