Library: General utilities
Does not inherit
A binary function or a function object that returns true or false. compare objects are typically passed as template parameters, and used for ordering elements within a container.
Use of the function objects equal_to and not_equal_to to order elements may give unexpected results.
binary_function, equal_to, not_equal_to, Function Objects
ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 25.3