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- [/
- Copyright 2018 Glen Joseph Fernandes
- (glenjofe@gmail.com)
- 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:enable_if enable_if_]
- template<bool B, class T = void>
- struct enable_if_;
- template<bool B, class T = void>
- using enable_if_t = typename enable_if_<B, T>::type;
- __type If `B` is true, then the member `type` is defined to be `T`. Otherwise
- there is no member `type`.
- __header `#include <boost/type_traits/enable_if.hpp>`
- [note The trait has the name `enable_if_` (with a trailing underscore) but
- behaves like `std::enable_if` or `boost::enable_if_c`. The existing trait
- with the name `boost::enable_if` has a different interface.]
- __examples
- The following function can be used to destroy each element of an array and
- specially handle arrays of trivially destructible types.
- template<class T>
- typename boost::enable_if_<!boost::has_trivial_destructor<T>::value>::type
- destroy(T* ptr, std::size_t size)
- {
- while (size > 0) {
- ptr[--size].~T();
- }
- }
- template<class T>
- typename boost::enable_if_<boost::has_trivial_destructor<T>::value>::type
- destroy(T*, std::size_t) { }
- [all_compilers] The type alias `enable_if_t` is only available if the compiler
- supports template aliases.
- [endsect]
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