std::is_copy_assignable, std::is_trivially_copy_assignable, std::is_nothrow_copy_assignable
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                    | Defined in header  <type_traits> | ||
| template< class T > struct is_copy_assignable; | (1) | (since C++11) | 
| template< class T > struct is_trivially_copy_assignable; | (2) | (since C++11) | 
| template< class T > struct is_nothrow_copy_assignable; | (3) | (since C++11) | 
1) Checks whether a type is CopyAssignable, i.e. has an accessible explicit or implicit copy assignment operator. If the requirement is met, a member constant value equal true is provided, otherwise value is false.
2) Same as 1), but evaluation of the copy-assignment expression will not call any operation that is not trivial.
3) Same as 1), but the evaluation of the copy-assignment expression will not call any operation that is not noexcept.
| Contents | 
Inherited from std::integral_constant
Member constants
| value [static] | true if Tis copy-assignable, false otherwise(public static member constant) | 
Member functions
| operator bool | converts the object to bool, returns value(public member function) | 
Member types
| Type | Definition | 
| value_type | bool | 
| type | std::integral_constant<bool, value> | 
[edit] Possible implementation
| template< class T> struct is_copy_assignable : std::is_assignable< typename std::add_lvalue_reference<T>::type, typename std::add_lvalue_reference<const T>::type> {}; template< class T> struct is_trivially_copy_assignable : std::is_trivially_assignable< typename std::add_lvalue_reference<T>::type, typename std::add_lvalue_reference<const T>::type> {}; template< class T> struct is_nothrow_copy_assignable : std::is_nothrow_assignable< typename std::add_lvalue_reference<T>::type, typename std::add_lvalue_reference<const T>::type> {}; | 
[edit] Example
Run this code
#include <iostream> #include <utility> #include <type_traits> struct Foo { int n; }; int main() { std::cout << std::boolalpha << "Foo is trivally copy-assignable? " << std::is_trivially_copy_assignable<Foo>::value << '\n' << "int[2] is copy-assignable? " << std::is_copy_assignable<int[2]>::value << '\n' << "int is nothrow copy-assignable? " << std::is_nothrow_copy_assignable<int>::value << '\n'; }
Output:
Foo is trivally copy-assignable? true int[2] is copy-assignable? false int is nothrow copy-assignable? true
[edit] See also
| (C++11)(C++11)(C++11) | checks if a type has a assignment operator for a specific argument (class template) | 
| (C++11)(C++11)(C++11) | checks if a type has a move assignment operator (class template) | 


