1 files changed, 179 insertions, 0 deletions
diff --git a/core/constexpr.hh b/core/constexpr.hh
new file mode 100644
index 0000000..559f8d1
--- /dev/null
+++ b/core/constexpr.hh
@@ -0,0 +1,179 @@
+#ifndef CORE_CONSTEXPR_HH
+#define CORE_CONSTEXPR_HH 1
+#pragma once
+
+namespace cxpr
+{
+template<typename T>
+constexpr static inline const T abs(const T x);
+template<typename T, std::size_t L>
+constexpr static inline const std::size_t array_size(const T(&)[L]);
+template<typename T, typename F>
+constexpr static inline const T ceil(const F x);
+template<typename T>
+constexpr static inline const T degrees(const T x);
+template<typename T, typename F>
+constexpr static inline const T floor(const F x);
+template<typename T>
+constexpr static inline const T clamp(const T x, const T min, const T max);
+template<typename T, typename F>
+constexpr static inline const T lerp(const T x, const T y, const F a);
+template<typename T>
+constexpr static inline const T log2(const T x);
+template<typename T>
+constexpr static inline const T max(const T x, const T y);
+template<typename T>
+constexpr static inline const T min(const T x, const T y);
+template<typename T>
+constexpr static inline const T mod_signed(const T x, const T m);
+template<typename T>
+constexpr static inline const T pow2(const T x);
+template<typename T>
+constexpr static inline const T radians(const T x);
+template<typename T>
+constexpr static inline const bool range(const T x, const T min, const T max);
+template<typename T, typename F>
+constexpr static inline const T sign(const F x);
+template<typename T, typename F>
+constexpr static inline const T smoothstep(const T x, const T y, const F a);
+} // namespace cxpr
+
+template<typename T>
+constexpr static inline const T cxpr::abs(const T x)
+{
+    if(x < static_cast<T>(0))
+        return -x;
+    return x;
+}
+
+template<typename T, std::size_t L>
+constexpr static inline const std::size_t cxpr::array_size(const T(&)[L])
+{
+    return L;
+}
+
+template<typename T, typename F>
+constexpr static inline const T cxpr::ceil(const F x)
+{
+    static_assert(std::is_integral_v<T>);
+    static_assert(std::is_floating_point_v<F>);
+
+    const T ival = static_cast<T>(x);
+    if(ival < x)
+        return ival + static_cast<T>(1);
+    return ival;
+}
+
+template<typename T>
+constexpr static inline const T cxpr::degrees(const T x)
+{
+    return x * static_cast<T>(180.0) / static_cast<T>(M_PI);
+}
+
+template<typename T, typename F>
+constexpr static inline const T cxpr::floor(const F x)
+{
+    static_assert(std::is_integral_v<T>);
+    static_assert(std::is_floating_point_v<F>);
+
+    const T ival = static_cast<T>(x);
+    if(ival > x)
+        return ival - static_cast<T>(1);
+    return ival;
+}
+
+template<typename T>
+constexpr static inline const T cxpr::clamp(const T x, const T min, const T max)
+{
+    if(x < min)
+        return min;
+    if(x > max)
+        return max;
+    return x;
+}
+
+template<typename T, typename F>
+constexpr static inline const T cxpr::lerp(const T x, const T y, const F a)
+{
+    static_assert(std::is_arithmetic_v<T>);
+    static_assert(std::is_floating_point_v<F>);
+    return static_cast<T>(static_cast<F>(x) * (static_cast<F>(1.0f) - a) + static_cast<F>(y) * a);
+}
+
+template<typename T>
+constexpr static inline const T cxpr::log2(const T x)
+{
+    if(x < 2)
+        return 0;
+    return cxpr::log2<T>((x + 1) >> 1) + 1;
+}
+
+template<typename T>
+constexpr static inline const T cxpr::max(const T x, const T y)
+{
+    if(x < y)
+        return y;
+    return x;
+}
+
+template<typename T>
+constexpr static inline const T cxpr::min(const T x, const T y)
+{
+    if(x > y)
+        return y;
+    return x;
+}
+
+template<typename T>
+constexpr static inline const T cxpr::mod_signed(const T x, const T m)
+{
+    static_assert(std::is_signed_v<T>);
+    static_assert(std::is_integral_v<T>);
+    const T result = static_cast<T>(x % m);
+    if(result < T(0))
+        return result + m;
+    return result;
+}
+
+template<typename T>
+constexpr static inline const T cxpr::pow2(const T x)
+{
+    T value = static_cast<T>(1);
+    while(value < x)
+        value *= static_cast<T>(2);
+    return value;
+}
+
+template<typename T>
+constexpr static inline const T cxpr::radians(const T x)
+{
+    return x * static_cast<T>(M_PI) / static_cast<T>(180.0);
+}
+
+template<typename T>
+constexpr static inline const bool cxpr::range(const T x, const T min, const T max)
+{
+    return ((x >= min) && (x <= max));
+}
+
+template<typename T, typename F>
+constexpr static inline const T cxpr::sign(const F x)
+{
+    if(x < F(0))
+        return T(-1);
+    if(x > F(0))
+        return T(+1);
+    return T(0);
+}
+
+template<typename T, typename F>
+constexpr static inline const T cxpr::smoothstep(const T x, const T y, const F a)
+{
+    static_assert(std::is_arithmetic_v<T>);
+    static_assert(std::is_floating_point_v<F>);
+
+    const F t = cxpr::clamp<F>((a - x) / (y - x), F(0), F(1));
+    return static_cast<T>(t * t * (F(3) - F(2) * t));
+}
+
+#endif /* CORE_CONSTEXPR_HH */