1 | // Boost.Range library |
2 | // |
3 | // Copyright Neil Groves 2014. Use, modification and |
4 | // distribution is subject to the Boost Software License, Version |
5 | // 1.0. (See accompanying file LICENSE_1_0.txt or copy at |
6 | // http://www.boost.org/LICENSE_1_0.txt) |
7 | // |
8 | // For more information, see http://www.boost.org/libs/range/ |
9 | // |
10 | #ifndef BOOST_RANGE_DETAIL_DEFAULT_CONSTRUCTIBLE_UNARY_FN_HPP_INCLUDED |
11 | #define BOOST_RANGE_DETAIL_DEFAULT_CONSTRUCTIBLE_UNARY_FN_HPP_INCLUDED |
12 | |
13 | #include <boost/optional/optional.hpp> |
14 | #include <boost/mpl/if.hpp> |
15 | #include <boost/type_traits/has_trivial_constructor.hpp> |
16 | |
17 | namespace boost |
18 | { |
19 | namespace range_detail |
20 | { |
21 | |
22 | template<typename F, typename R> |
23 | class default_constructible_unary_fn_wrapper |
24 | { |
25 | public: |
26 | typedef R result_type; |
27 | |
28 | default_constructible_unary_fn_wrapper() |
29 | { |
30 | } |
31 | default_constructible_unary_fn_wrapper(const F& source) |
32 | : m_impl(source) |
33 | { |
34 | } |
35 | template<typename Arg> |
36 | R operator()(const Arg& arg) const |
37 | { |
38 | BOOST_ASSERT(m_impl); |
39 | return (*m_impl)(arg); |
40 | } |
41 | template<typename Arg> |
42 | R operator()(Arg& arg) const |
43 | { |
44 | BOOST_ASSERT(m_impl); |
45 | return (*m_impl)(arg); |
46 | } |
47 | private: |
48 | boost::optional<F> m_impl; |
49 | }; |
50 | |
51 | template<typename F, typename R> |
52 | struct default_constructible_unary_fn_gen |
53 | { |
54 | typedef typename boost::mpl::if_< |
55 | boost::has_trivial_default_constructor<F>, |
56 | F, |
57 | default_constructible_unary_fn_wrapper<F,R> |
58 | >::type type; |
59 | }; |
60 | |
61 | } // namespace range_detail |
62 | } // namespace boost |
63 | |
64 | #endif // include guard |
65 | |