Ion Gaztañaga — Mon, 16 Jan 2017 00:28:27 GMT

This should have been fixed in Boost 1.62. See ticket 11994 for details:

https://svn.boost.org/trac/boost/ticket/11994

fdegros@… — Tue, 17 Jan 2017 00:24:13 GMT

Maybe the documentation needs to be updated.

See http://www.boost.org/doc/libs/1_63_0/doc/html/intrusive/map_multimap.html. It still specifies that the key extractor must have a "member function to obtain a const reference to the key stored inside a value_type".

The example also emphasizes that a reference must be returned. This could be updated, especially since the example function returns an int.

Example:

// key_of_value function object, must:
// - be default constructible (and lightweight)
// - define the key type by defining a nested type called "type"
// - define an operator() taking "const value_type&" and
//     returning "type" or "const type &"
struct first_int_is_key
{
   typedef int type;
   type operator()(const MyClass& v) const {  return v.first;  }
};

Ion Gaztañaga — Mon, 06 Feb 2017 12:21:43 GMT

Thanks. Documentation fixed in commit:

https://github.com/boostorg/intrusive/commit/6fe118157867ea26109447ad5eeaaa02fb2dce57

Boost C++ Libraries: Ticket #12721: intrusive key_of_value requires value to be returned by reference