// 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_SAFE_COMPARISON_HPP #define BOOST_HISTOGRAM_DETAIL_SAFE_COMPARISON_HPP #include <boost/mp11/utility.hpp> #include <boost/type.hpp> #include <type_traits> namespace boost { namespace histogram { namespace detail { template <class T> auto make_unsigned(const T& t) noexcept { static_assert(std::is_integral<T>::value, ""); return static_cast<std::make_unsigned_t<T>>(t); } template <class T> using number_category = mp11::mp_if<std::is_integral<T>, mp11::mp_if<std::is_signed<T>, type<int>, type<unsigned>>, type<void>>; // version of std::equal_to<> which handles signed and unsigned integers correctly struct safe_equal { template <class T, class U> bool operator()(const T& t, const U& u) const noexcept { return impl(number_category<T>{}, number_category<U>{}, t, u); } template <class C1, class C2, class T, class U> bool impl(C1, C2, const T& t, const U& u) const noexcept { return t == u; } template <class T, class U> bool impl(type<int>, type<unsigned>, const T& t, const U& u) const noexcept { return t >= 0 && make_unsigned(t) == u; } template <class T, class U> bool impl(type<unsigned>, type<int>, const T& t, const U& u) const noexcept { return impl(type<int>{}, type<unsigned>{}, u, t); } }; // version of std::less<> which handles signed and unsigned integers correctly struct safe_less { template <class T, class U> bool operator()(const T& t, const U& u) const noexcept { return impl(number_category<T>{}, number_category<U>{}, t, u); } template <class C1, class C2, class T, class U> bool impl(C1, C2, const T& t, const U& u) const noexcept { return t < u; } template <class T, class U> bool impl(type<int>, type<unsigned>, const T& t, const U& u) const noexcept { return t < 0 || make_unsigned(t) < u; } template <class T, class U> bool impl(type<unsigned>, type<int>, const T& t, const U& u) const noexcept { return 0 < u && t < make_unsigned(u); } }; // version of std::greater<> which handles signed and unsigned integers correctly struct safe_greater { template <class T, class U> bool operator()(const T& t, const U& u) const noexcept { return safe_less()(u, t); } }; } // namespace detail } // namespace histogram } // namespace boost #endif