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- [/
- Copyright 2007 John Maddock.
- Copyright 2014 Ion Gaztanaga.
- 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_copy_assignable is_copy_assignable]
- template <class T>
- struct is_copy_assignable : public __tof {};
-
- __inherit If `T` is `CopyAssignable` (i.e. has an accessible explicit or implicit copy assignment operator),
- then inherits from __true_type, otherwise inherits from __false_type. Type `T`
- must be a complete type.
- In other words, inherits from __true_type only if copy assignment of `T` from `const T &` is not
- marked with `= delete`, `T` does not derives from `boost::noncopyable` and
- is not marked with `BOOST_MOVABLE_BUT_NOT_COPYABLE(T)`.
- __compat Requires the C++11 features `decltype` and SFINAE-expressions for full support.
- If your compiler does not support C++11 deleted functions (`= delete`) or does not support
- SFINAE for the deleted assignments, then derive your classes from `boost::noncopyable` or
- mark them with `BOOST_MOVABLE_BUT_NOT_COPYABLE(T)` to show that class is non-assignable.
- Trait does not care about access modifiers, so if you see errors like this:
- 'T::operator=(const T&)' is private
- boost/type_traits/is_copy_assignable.hpp:68:5: error: within this context
- then you are trying to call that macro for a structure with private assignment:
- struct T {
- // ...
- private:
- T &operator=(const T &);
- // ...
- };
- To fix that you must modify your structure, explicitly marking it as noncopyable (`= delete`,
- `boost::noncopyable` or `BOOST_MOVABLE_BUT_NOT_COPYABLE(T)`) or explicitly
- [link boost_typetraits.user_defined specializing the trait].
- __header ` #include <boost/type_traits/is_copy_assignable.hpp>` or ` #include <boost/type_traits.hpp>`
- [endsect]
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