Re: [Boost-users] [Unordered] [Multi-Index] Set lookup from something else than key_type

Am Wednesday 02 September 2009 12:47:56 schrieb Daniel James:

But those overloads don't always exist. A simple example is:

struct hash { std::size_t operator()(std::string const&) const; };

struct equals { bool operator()(std::string const&, std::string const&) const; };

boost::unordered_map map; // .... map.find("char array");

A single string object should be created in this case.

Boost.Intrusive implements this type of feature in its intrusive unordered set: http://www.boost.org/doc/libs/1_40_0/doc/html/boost/intrusive/unordered_set.... and I just recently had to use a unordered_map instead of a unordered_set<mapped>, even though the key is obtainable from mapped, because mapped is not constructible from key.