add lightweight alternative to std:numeric_limits

1 files changed, 39 insertions, 1 deletions

diff --git a/compat/limits.hpp b/compat/limits.hpp
index ec1b67a8..0de74afa 100644
--- a/compat/limits.hpp
+++ b/compat/limits.hpp
@@ -1,3 +1,41 @@
 #pragma once
 
-// add things from numeric_limits for {u,}ints and floats/doubles/long doubles
+namespace floormat {
+
+template<typename T> struct limits;
+
+template<typename T>
+requires (std::is_signed_v<T> && std::is_integral_v<T>)
+struct limits<T>
+{
+    using Type = T;
+    static constexpr T min{-int64_t{1} << sizeof(T)*8-1}, max{-(min+1)};
+};
+
+template<typename T>
+requires (std::is_unsigned_v<T>)
+struct limits<T>
+{
+    using Type = T;
+    static_assert(std::is_integral_v<T>);
+    static constexpr T min{0}, max{T(-1)};
+};
+
+template<> struct limits<float>
+{
+    using Type = float;
+    static constexpr float max{1 << 24}, min{-max};
+    using integer_type = int32_t;
+};
+
+template<> struct limits<double>
+{
+    using Type = double;
+    static constexpr double max = double{uint64_t{1} << 53}, min{-max};
+    using integer_type = int64_t;
+};
+
+template<typename T> requires std::is_arithmetic_v<T> using int_max = typename limits<T>::max;;
+template<typename T> requires std::is_arithmetic_v<T> using int_min = typename limits<T>::min;;
+
+} // namespace floormat