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- // Copyright 2019 Hans Dembinski
- //
- // 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)
- #ifndef BOOST_HISTOGRAM_DETAIL_TRY_CAST_HPP
- #define BOOST_HISTOGRAM_DETAIL_TRY_CAST_HPP
- #include <boost/config.hpp>
- #include <boost/core/demangle.hpp>
- #include <boost/histogram/detail/type_name.hpp>
- #include <boost/mp11/integral.hpp>
- #include <boost/throw_exception.hpp>
- #include <stdexcept>
- #include <string>
- #include <type_traits>
- namespace boost {
- namespace histogram {
- namespace detail {
- template <class T, class E, class U>
- BOOST_NORETURN T try_cast_impl(mp11::mp_int<0>, U&&) {
- BOOST_THROW_EXCEPTION(E("cannot cast " + type_name<T>() + " to " + type_name<U>()));
- }
- template <class T, class E, class U>
- T try_cast_impl(mp11::mp_int<1>, U&& u) noexcept {
- return static_cast<T>(u);
- }
- template <class T, class E, class U>
- decltype(auto) try_cast_impl(mp11::mp_int<2>, U&& u) noexcept {
- return std::forward<U>(u);
- }
- // cast fails at runtime with exception E instead of compile-time, T must be a value
- template <class T, class E, class U>
- decltype(auto) try_cast(U&& u) noexcept(std::is_convertible<U, T>::value) {
- return try_cast_impl<T, E>(mp11::mp_int<(std::is_convertible<U, T>::value +
- std::is_same<T, std::decay_t<U>>::value)>{},
- std::forward<U>(u));
- }
- } // namespace detail
- } // namespace histogram
- } // namespace boost
- #endif
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