Added thirdparty: boost library

thirdparty/include/boost/histogram/detail/safe_comparison.hpp

@@ -0,0 +1,87 @@
+// 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