template <class T> struct is_nothrow_move_assignable : public
is a (possibly cv-qualified) type with a non-throwing move assignment-operator
or a type without move assignment-operator but with non-throwing assignment-operator,
then inherits from true_type,
otherwise inherits from false_type.
T must be a complete
In other words, inherits from true_type
only if expression
variable1 = std::move(variable2) won't throw (
variable2 are variables
Compiler Compatibility: If the compiler does not support partial-specialization of class templates, then this template can not be used with function types.
Without some (C++11 noexcept shall work correctly) help from the compiler,
will never report that a class or struct has a non-throwing assignment-operator;
this is always safe, if possibly sub-optimal. Currently (February 2013) Clang
and GCC 4.7 have the necessary compiler support to ensure that this trait