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

Date: Mon, 04 Apr 2005 16:39:34 +0100 From: Ben Hutchings Subject: Re: [Boost-users] Re: unordered_map has no lower_bound? To: boost-users@lists.boost.org Message-ID: <42515FB6.9040803@businesswebsoftware.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Daniel James wrote:

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Martin Wartens wrote:

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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.

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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.

I always use !! to prevent that warning. like return !!*prev_ptr; YMMV.