For a non-virtual member function described in the C++ standard library,
an implementation may declare a different set of member function signatures,
provided that any call to the member function that would select
an overload from the set of declarations described in this document
behaves as if that overload were selected.
For instance, an implementation can add parameters with default values,
or replace a member function with default arguments
with two or more member functions with equivalent behavior,
or add additional signatures for a member function name.