88 lines
2.5 KiB
C++
88 lines
2.5 KiB
C++
// Copyright 2019 Hans Dembinski
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//
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// Distributed under the Boost Software License, Version 1.0.
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// (See accompanying file LICENSE_1_0.txt
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// or copy at http://www.boost.org/LICENSE_1_0.txt)
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#ifndef BOOST_HISTOGRAM_DETAIL_SAFE_COMPARISON_HPP
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#define BOOST_HISTOGRAM_DETAIL_SAFE_COMPARISON_HPP
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#include <boost/mp11/utility.hpp>
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#include <boost/type.hpp>
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#include <type_traits>
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namespace boost {
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namespace histogram {
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namespace detail {
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template <class T>
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auto make_unsigned(const T& t) noexcept {
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static_assert(std::is_integral<T>::value, "");
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return static_cast<std::make_unsigned_t<T>>(t);
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}
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template <class T>
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using number_category =
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mp11::mp_if<std::is_integral<T>,
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mp11::mp_if<std::is_signed<T>, type<int>, type<unsigned>>, type<void>>;
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// version of std::equal_to<> which handles signed and unsigned integers correctly
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struct safe_equal {
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template <class T, class U>
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bool operator()(const T& t, const U& u) const noexcept {
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return impl(number_category<T>{}, number_category<U>{}, t, u);
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}
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template <class C1, class C2, class T, class U>
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bool impl(C1, C2, const T& t, const U& u) const noexcept {
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return t == u;
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}
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template <class T, class U>
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bool impl(type<int>, type<unsigned>, const T& t, const U& u) const noexcept {
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return t >= 0 && make_unsigned(t) == u;
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}
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template <class T, class U>
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bool impl(type<unsigned>, type<int>, const T& t, const U& u) const noexcept {
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return impl(type<int>{}, type<unsigned>{}, u, t);
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}
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};
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// version of std::less<> which handles signed and unsigned integers correctly
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struct safe_less {
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template <class T, class U>
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bool operator()(const T& t, const U& u) const noexcept {
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return impl(number_category<T>{}, number_category<U>{}, t, u);
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}
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template <class C1, class C2, class T, class U>
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bool impl(C1, C2, const T& t, const U& u) const noexcept {
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return t < u;
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}
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template <class T, class U>
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bool impl(type<int>, type<unsigned>, const T& t, const U& u) const noexcept {
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return t < 0 || make_unsigned(t) < u;
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}
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template <class T, class U>
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bool impl(type<unsigned>, type<int>, const T& t, const U& u) const noexcept {
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return 0 < u && t < make_unsigned(u);
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}
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};
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// version of std::greater<> which handles signed and unsigned integers correctly
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struct safe_greater {
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template <class T, class U>
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bool operator()(const T& t, const U& u) const noexcept {
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return safe_less()(u, t);
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}
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};
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} // namespace detail
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} // namespace histogram
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} // namespace boost
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#endif
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