Wrapped direct use of C++20 library concepts

Some C++ libraries do not fully support concepts in the versions that
are available by default on Linux and MacOS. The compilers do support
them though so we can still apply concepts/requires to templates

6 files changed, 31 insertions, 8 deletions

diff --git a/zencore/include/zencore/intmath.h b/zencore/include/zencore/intmath.h
index 0d0ceff16..b4a0b6796 100644
--- a/zencore/include/zencore/intmath.h
+++ b/zencore/include/zencore/intmath.h
@@ -59,7 +59,7 @@ IsPow2(uint64_t n)
 }
 
 /// Round an integer up to the closest integer multiplier of 'base' ('base' must be a power of two)
-template<std::integral T>
+template<Integral T>
 T
 RoundUp(T Value, auto Base)
 {
@@ -68,7 +68,7 @@ RoundUp(T Value, auto Base)
 }
 
 bool
-IsMultipleOf(std::integral auto Value, auto MultiplierPow2)
+IsMultipleOf(Integral auto Value, auto MultiplierPow2)
 {
 	ZEN_ASSERT_SLOW(IsPow2(MultiplierPow2));
 	return (Value & (MultiplierPow2 - 1)) == 0;
diff --git a/zencore/include/zencore/refcount.h b/zencore/include/zencore/refcount.h
index e8a3095f9..5c8b70ef6 100644
--- a/zencore/include/zencore/refcount.h
+++ b/zencore/include/zencore/refcount.h
@@ -118,7 +118,7 @@ public:
 	inline ~Ref() { m_Ref && m_Ref->Release(); }
 
 	template<typename DerivedType>
-	requires std::derived_from<DerivedType, T>
+	requires DerivedFrom<DerivedType, T>
 	inline Ref(const Ref<DerivedType>& Rhs) : Ref(Rhs.m_Ref) {}
 
 	[[nodiscard]] inline bool IsNull() const { return m_Ref == nullptr; }
diff --git a/zencore/include/zencore/sharedbuffer.h b/zencore/include/zencore/sharedbuffer.h
index 1f87dc639..97c5a9d21 100644
--- a/zencore/include/zencore/sharedbuffer.h
+++ b/zencore/include/zencore/sharedbuffer.h
@@ -144,7 +144,7 @@ public:
 	/** Make a non-owned view of the input */
 	[[nodiscard]] inline static SharedBuffer MakeView(MemoryView View) { return MakeView(View.GetData(), View.GetSize()); }
 	/** Make a non-owning view of the memory of the contiguous container. */
-	[[nodiscard]] inline static SharedBuffer MakeView(const std::ranges::contiguous_range auto& Container)
+	[[nodiscard]] inline static SharedBuffer MakeView(const ContiguousRange auto& Container)
 	{
 		std::span Span = Container;
 		return MakeView(Span.data(), Span.size() * sizeof(typename decltype(Span)::element_type));
diff --git a/zencore/include/zencore/stats.h b/zencore/include/zencore/stats.h
index d58435a20..f0efc36d8 100644
--- a/zencore/include/zencore/stats.h
+++ b/zencore/include/zencore/stats.h
@@ -142,7 +142,7 @@ public:
 	void		   Update(int64_t Value);
 	SampleSnapshot Snapshot() const;
 
-	template<std::invocable<int64_t> T>
+	template<Invocable<int64_t> T>
 	void IterateValues(T Callback) const
 	{
 		for (const auto& Value : m_Values)
diff --git a/zencore/include/zencore/string.h b/zencore/include/zencore/string.h
index 848310aa3..df78b2757 100644
--- a/zencore/include/zencore/string.h
+++ b/zencore/include/zencore/string.h
@@ -74,8 +74,8 @@ protected:
 
 struct IntNum : public TextNumBase
 {
-	inline IntNum(std::unsigned_integral auto Number) { ToString(m_Buffer, uint64_t(Number)); }
-	inline IntNum(std::signed_integral auto Number) { ToString(m_Buffer, int64_t(Number)); }
+	inline IntNum(UnsignedIntegral auto Number) { ToString(m_Buffer, uint64_t(Number)); }
+	inline IntNum(SignedIntegral auto Number) { ToString(m_Buffer, int64_t(Number)); }
 };
 
 //////////////////////////////////////////////////////////////////////////
@@ -602,7 +602,7 @@ NiceRate(uint64_t Num, uint32_t DurationMilliseconds, const char* Unit = "B")
 
 //////////////////////////////////////////////////////////////////////////
 
-template<std::integral T>
+template<Integral T>
 std::optional<T>
 ParseInt(const std::string_view& Input)
 {
diff --git a/zencore/include/zencore/zencore.h b/zencore/include/zencore/zencore.h
index 3352af5d2..8688ddc13 100644
--- a/zencore/include/zencore/zencore.h
+++ b/zencore/include/zencore/zencore.h
@@ -5,6 +5,7 @@
 #include <cinttypes>
 #include <stdexcept>
 #include <string>
+#include <version>
 
 #ifndef ZEN_WITH_TESTS
 #	define ZEN_WITH_TESTS 1
@@ -119,6 +120,28 @@
 		} while (0)
 #endif
 
+// At the time of writing only ver >= 13 of LLVM's libc++ has an implementation
+// of std::integral. Some platforms like Ubuntu and Mac OS are still on 12.
+#if defined(__cpp_lib_concepts)
+	template <class T> concept Integral				 = std::integral<T>;
+	template <class T> concept SignedIntegral		 = std::signed_integral<T>;
+	template <class T> concept UnsignedIntegral		 = std::unsigned_integral<T>;
+	template <class F, class... A> concept Invocable = std::invocable<F, A...>;
+	template <class D, class B> concept DerivedFrom	 = std::derived_from<D, B>;
+#else
+	template <class T> concept Integral				 = std::is_integral_v<T>;
+	template <class T> concept SignedIntegral		 = Integral<T> &&  std::is_signed_v<T>;
+	template <class T> concept UnsignedIntegral		 = Integral<T> && !std::is_signed_v<T>;
+	template <class F, class... A> concept Invocable = true;
+	template <class D, class B> concept DerivedFrom	 = std::is_base_of_v<B, D> && std::is_convertible_v<const volatile D*, const volatile B*>;
+#endif
+
+#if defined(__cpp_lib_ranges)
+	template <typename T> concept ContiguousRange = std::ranges::contiguous_range<T>;
+#else
+	template <typename T> concept ContiguousRange = true;
+#endif
+
 //////////////////////////////////////////////////////////////////////////
 // Architecture
 //