Boost
C++ Libraries
...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
Boost
C++ Libraries
...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
template <class T, class U>
struct is_assignable : public true_type-or-false_type {};
Inherits: If std::declval<T>()
= std::declval<U>()
then inherits from true_type,
otherwise from false_type.
Type T must be a complete
type.
Note that this trait is somewhat tricky to use correctly: for example:
is_assignable<int, int>::value
is false since std::declval<int>()
is an xvalue which can not be assigned to!
If you're intention is to check for copy-assignment from some type U then use:
is_assignable<T&, const U&>::value
If you're intention is to check for move-assignment then use:
is_assignable<T&, U&&>::value
or simply:
is_assignable<T&, U>::value
Compiler Compatibility: Requires the C++11
features decltype and SFINAE-expressions
for full support.
Header: #include
<boost/type_traits/is_assignable.hpp>
or #include <boost/type_traits.hpp>