From b18061ab0ee2f54528edb6ac357a831184736c8d Mon Sep 17 00:00:00 2001
From: Mateusz Pusz <mateusz.pusz@gmail.com>
Date: Sun, 21 Feb 2021 00:40:56 +0100
Subject: [PATCH] build: clang support added

---
 conanfile.py                            |  12 ++-
 src/CMakeLists.txt                      |   1 +
 src/include/units/bits/external/hacks.h | 119 +++++++++++++++++++++++-
 3 files changed, 124 insertions(+), 8 deletions(-)

diff --git a/conanfile.py b/conanfile.py
index 38d5582f..87080e65 100644
--- a/conanfile.py
+++ b/conanfile.py
@@ -86,13 +86,15 @@ class UnitsConan(ConanFile):
         if compiler == "gcc":
             if version < "10.0":
                 raise ConanInvalidConfiguration("mp-units requires at least g++-10")
+        elif compiler == "clang":
+            if version < "12":
+                raise ConanInvalidConfiguration("mp-units requires at least clang++-12")
         elif compiler == "Visual Studio":
             if version < "16":
                 raise ConanInvalidConfiguration("mp-units requires at least Visual Studio 16.7")
         else:
-            raise ConanInvalidConfiguration("mp-units is supported only by gcc and Visual Studio so far")
-        if compiler.get_safe("cppstd"):
-            check_min_cppstd(self, "20")
+            raise ConanInvalidConfiguration("Unsupported compiler")
+        check_min_cppstd(self, "20")
 
     # TODO Uncomment this when environment is supported in the Conan toolchain
     # def config_options(self):
@@ -100,6 +102,10 @@ class UnitsConan(ConanFile):
     #         # build_docs has sense only in a development or CI build
     #         del self.options.build_docs
 
+    def requirements(self):
+        if self.settings.compiler == "clang":
+            self.requires("range-v3/0.11.0")
+
     def build_requirements(self):
         if self._run_tests:
             self.build_requires("catch2/2.13.4")
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 8416b741..c73d7254 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -51,6 +51,7 @@ target_include_directories(mp-units
 )
 
 if(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+    find_package(range-v3)
     target_link_libraries(mp-units
         INTERFACE
             range-v3::range-v3
diff --git a/src/include/units/bits/external/hacks.h b/src/include/units/bits/external/hacks.h
index 28f781b9..b5f0a517 100644
--- a/src/include/units/bits/external/hacks.h
+++ b/src/include/units/bits/external/hacks.h
@@ -22,8 +22,6 @@
 
 #pragma once
 
-#include <concepts>
-
 #if __clang__
 #define COMP_CLANG __clang_major__
 #elif __GNUC__
@@ -33,7 +31,18 @@
 #define COMP_MSVC _MSC_VER
 #endif
 
-#if COMP_MSVC
+#if COMP_CLANG
+
+#include <concepts/compare.hpp>
+#include <concepts/concepts.hpp>
+#include <range/v3/functional/comparisons.hpp>
+
+#endif
+
+#include <concepts>
+#include <compare>
+
+#if COMP_MSVC || COMP_CLANG
 
 #define TYPENAME typename
 
@@ -43,13 +52,113 @@
 
 #endif
 
-#if COMP_GCC
 
 namespace std {
 
+#if COMP_GCC
+
 template<class T>
 concept default_constructible = constructible_from<T>;
 
-} // namespace std
+#elif COMP_CLANG
+
+// concepts
+using concepts::three_way_comparable;
+using concepts::three_way_comparable_with;
+// using concepts::common_reference_with;
+using concepts::common_with;
+using concepts::constructible_from;
+using concepts::convertible_to;
+// using concepts::default_constructible;
+using concepts::derived_from;
+// using concepts::equality_comparable;
+using concepts::equality_comparable_with;
+// // using concepts::floating_point;
+// using concepts::integral;
+using concepts::regular;
+// using concepts::same_as;
+// using concepts::totally_ordered;
+// using concepts::totally_ordered_with;
+
+using ranges::compare_three_way;
+
+// namespace ranges {
+
+// using ::ranges::forward_range;
+// using ::ranges::range_value_t;
+
+// }
+
+// // missing in Range-v3
+// template<class T>
+// concept floating_point = std::is_floating_point_v<T>;
+
+template<class F, class... Args>
+concept invocable =
+requires(F&& f, Args&&... args) {
+  std::invoke(std::forward<F>(f), std::forward<Args>(args)...);
+};
+
+template<class F, class... Args>
+concept regular_invocable = invocable<F, Args...>;
+
+template<class T, class U>
+constexpr bool cmp_equal(T t, U u) noexcept
+{
+  using UT = std::make_unsigned_t<T>;
+  using UU = std::make_unsigned_t<U>;
+  if constexpr (std::is_signed_v<T> == std::is_signed_v<U>)
+      return t == u;
+  else if constexpr (std::is_signed_v<T>)
+      return t < 0 ? false : UT(t) == u;
+  else
+      return u < 0 ? false : t == UU(u);
+}
+ 
+template<class T, class U>
+constexpr bool cmp_not_equal(T t, U u) noexcept
+{
+  return !cmp_equal(t, u);
+}
+ 
+template<class T, class U>
+constexpr bool cmp_less(T t, U u) noexcept
+{
+  using UT = std::make_unsigned_t<T>;
+  using UU = std::make_unsigned_t<U>;
+  if constexpr (std::is_signed_v<T> == std::is_signed_v<U>)
+      return t < u;
+  else if constexpr (std::is_signed_v<T>)
+      return t < 0 ? true : UT(t) < u;
+  else
+      return u < 0 ? false : t < UU(u);
+}
+ 
+template<class T, class U>
+constexpr bool cmp_greater(T t, U u) noexcept
+{
+  return cmp_less(u, t);
+}
+ 
+template<class T, class U>
+constexpr bool cmp_less_equal(T t, U u) noexcept
+{
+  return !cmp_greater(t, u);
+}
+ 
+template<class T, class U>
+constexpr bool cmp_greater_equal(T t, U u) noexcept
+{
+  return !cmp_less(t, u);
+}
+
+template<class R, class T>
+constexpr bool in_range(T t) noexcept
+{
+  return std::cmp_greater_equal(t, std::numeric_limits<R>::min()) &&
+        std::cmp_less_equal(t, std::numeric_limits<R>::max());
+}
 
 #endif
+
+} // namespace std