Boost C++ Libraries

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has_trivial_assign

template <class T>
struct has_trivial_assign : public true_type-or-false_type {};

Inherits: If T is a (possibly cv-qualified) type with a trivial assignment-operator then inherits from true_type, otherwise inherits from false_type.

If a type has a trivial assignment-operator then the operator has the same effect as copying the bits of one object to the other: calls to the operator can be safely replaced with a call to memcpy.

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 (as yet unspecified) help from the compiler, has_trivial_assign will never report that a user-defined class or struct has a trivial constructor; this is always safe, if possibly sub-optimal. Currently (May 2011) compilers more recent than Visual C++ 8, GCC-4.3, Greenhills 6.0, Intel-11.0, and Codegear have the necessary compiler intrinsics to ensure that this trait "just works". You may also test to see if the necessary intrinsics are available by checking to see if the macro BOOST_HAS_TRIVIAL_ASSIGN is defined.

C++ Standard Reference: 12.8p11.

Header: #include <boost/type_traits/has_trivial_assign.hpp> or #include <boost/type_traits.hpp>

Examples:

has_trivial_assign<int> inherits from true_type.

has_trivial_assign<char*>::type is the type true_type.

has_trivial_assign<int (*)(long)>::value is an integral constant expression that evaluates to true.

has_trivial_assign<MyClass>::value is an integral constant expression that evaluates to false.

has_trivial_assign<T>::value_type is the type bool.


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