Re: [Boost-users] Re: unordered_map has no lower_bound?

From: Ben Hutchings (ben.hutchings_at_[hidden])
Date: 2005-04-04 10:39:34

Daniel James wrote:
>> Martin Wartens wrote:
>>
>>> PS: there is a small problem in hash_table.hpp causing a warning in 
>>> VC7.1
>>> line 278 should be:
>>> return (*prev_ptr)!=0;
>>> instead of
>>> return *prev_ptr;
> 
> 
> Ah, I just found out why I didn't do this before - prev_ptr might be a 
> pointer object (depending on the allocator), so the correct line is:
> 
> return (*prev_ptr) != link_ptr();
> 
> Which can potentially be inefficient. I think the best thing to do is to 
> use a pragma to disable the warning,

If it's the warning I'm thinking of (C4800: "forcing value to bool 
'true' or 'false'" - well, *duh*) then this is the right approach.

 > or maybe:
> 
>     return static_cast<bool>(*prev_ptr);
> 
> or:
> 
>     return boost::implicit_cast<bool>(*prev_ptr);
> 
> would work.

Neither of those prevents the warning.

Ben.