12345678910111213141516171819202122232425262728293031323334353637383940 |
- [/
- Copyright 2015 John Maddock.
- Distributed under the Boost Software License, Version 1.0.
- (See accompanying file LICENSE_1_0.txt or copy at
- http://www.boost.org/LICENSE_1_0.txt).
- ]
- [section:is_assignable is_assignable]
- template <class T, class U>
- struct is_assignable : public __tof {};
-
- __inherit 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
- __compat 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>`
- [endsect]
|