Re: [Boost-users] shared_ptr to object in stl set container?

n 13 December 2011 13:38, Lars Viklund wrote:

On Tue, Dec 13, 2011 at 12:52:33PM +0000, Rob Desbois wrote:

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On 13 December 2011 10:07, Igor R wrote:

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-- I'm trying to use shared_ptr in a stl set, but am having trouble with find() Any help? Documentation on this seems hard to find.

-- Also, are the overloaded < and == useful or correct here?

No, std algorithms won't call your comparison operators, because those of boost::shared_ptr do not compare pointees. You can define in your cpp something like this (operator ==() is not needed for your particular case):

operator<() is needed for set sorting, but he does need operator==() for the find() to work.

Sets do not "need" op<. The default comparator template argument is std::less<K>, which has a fallback implementation using op< for things not explicitly specialized.

Apologies - what I meant included that, though was unclear.

std::set<K>::find doesn't use op==. It uses the comparator in a fashion akin to !(key_comp(a,b) || key_comp(b,a)), that is, if neither key is less than the other, it's by necessity equivalent.

Ah, I didn't know that, though it makes sense thinking about it. Thanks :-) -- Rob Desbois Blog: http://theotherbranch.wordpress.com/ "I disapprove of what you say, but I’ll defend to the death your right to say it", Voltaire