From 6dd7edd2e0208d7bb38a803ffa0d18b6ada9edf6 Mon Sep 17 00:00:00 2001
From: Chris Robinson <chris.kcat@gmail.com>
Date: Thu, 30 Jun 2022 00:35:30 -0700
Subject: Make some Vector and Matrix methods constexpr

---
 common/vecmat.h | 51 ++++++++++++++++++++++-----------------------------
 1 file changed, 22 insertions(+), 29 deletions(-)

(limited to 'common/vecmat.h')

diff --git a/common/vecmat.h b/common/vecmat.h
index 78fd806e..a45f262f 100644
--- a/common/vecmat.h
+++ b/common/vecmat.h
@@ -14,19 +14,19 @@ namespace alu {
 template<typename T>
 class VectorR {
     static_assert(std::is_floating_point<T>::value, "Must use floating-point types");
-    alignas(16) std::array<T,4> mVals;
+    alignas(16) T mVals[4];
 
 public:
     constexpr VectorR() noexcept = default;
     constexpr VectorR(const VectorR&) noexcept = default;
-    constexpr VectorR(T a, T b, T c, T d) noexcept : mVals{{a, b, c, d}} { }
+    constexpr explicit VectorR(T a, T b, T c, T d) noexcept : mVals{a, b, c, d} { }
 
     constexpr VectorR& operator=(const VectorR&) noexcept = default;
 
-    T& operator[](size_t idx) noexcept { return mVals[idx]; }
+    constexpr T& operator[](size_t idx) noexcept { return mVals[idx]; }
     constexpr const T& operator[](size_t idx) const noexcept { return mVals[idx]; }
 
-    VectorR& operator+=(const VectorR &rhs) noexcept
+    constexpr VectorR& operator+=(const VectorR &rhs) noexcept
     {
         mVals[0] += rhs.mVals[0];
         mVals[1] += rhs.mVals[1];
@@ -35,14 +35,13 @@ public:
         return *this;
     }
 
-    VectorR operator-(const VectorR &rhs) const noexcept
+    constexpr VectorR operator-(const VectorR &rhs) const noexcept
     {
-        const VectorR ret{mVals[0] - rhs.mVals[0], mVals[1] - rhs.mVals[1],
+        return VectorR{mVals[0] - rhs.mVals[0], mVals[1] - rhs.mVals[1],
             mVals[2] - rhs.mVals[2], mVals[3] - rhs.mVals[3]};
-        return ret;
     }
 
-    T normalize(T limit = std::numeric_limits<T>::epsilon())
+    constexpr T normalize(T limit = std::numeric_limits<T>::epsilon())
     {
         limit = std::max(limit, std::numeric_limits<T>::epsilon());
         const T length_sqr{mVals[0]*mVals[0] + mVals[1]*mVals[1] + mVals[2]*mVals[2]};
@@ -59,38 +58,39 @@ public:
         return T{0};
     }
 
-    constexpr VectorR cross_product(const alu::VectorR<T> &rhs) const
+    constexpr VectorR cross_product(const alu::VectorR<T> &rhs) const noexcept
     {
         return VectorR{
-            (*this)[1]*rhs[2] - (*this)[2]*rhs[1],
-            (*this)[2]*rhs[0] - (*this)[0]*rhs[2],
-            (*this)[0]*rhs[1] - (*this)[1]*rhs[0],
+            mVals[1]*rhs.mVals[2] - mVals[2]*rhs.mVals[1],
+            mVals[2]*rhs.mVals[0] - mVals[0]*rhs.mVals[2],
+            mVals[0]*rhs.mVals[1] - mVals[1]*rhs.mVals[0],
             T{0}};
     }
 
-    constexpr T dot_product(const alu::VectorR<T> &rhs) const
-    { return (*this)[0]*rhs[0] + (*this)[1]*rhs[1] + (*this)[2]*rhs[2]; }
+    constexpr T dot_product(const alu::VectorR<T> &rhs) const noexcept
+    { return mVals[0]*rhs.mVals[0] + mVals[1]*rhs.mVals[1] + mVals[2]*rhs.mVals[2]; }
 };
 using Vector = VectorR<float>;
 
 template<typename T>
 class MatrixR {
     static_assert(std::is_floating_point<T>::value, "Must use floating-point types");
-    alignas(16) std::array<T,16> mVals;
+    alignas(16) T mVals[16];
 
 public:
     constexpr MatrixR() noexcept = default;
     constexpr MatrixR(const MatrixR&) noexcept = default;
-    constexpr MatrixR(T aa, T ab, T ac, T ad,
-                      T ba, T bb, T bc, T bd,
-                      T ca, T cb, T cc, T cd,
-                      T da, T db, T dc, T dd) noexcept
-      : mVals{{aa,ab,ac,ad, ba,bb,bc,bd, ca,cb,cc,cd, da,db,dc,dd}}
+    constexpr explicit MatrixR(
+        T aa, T ab, T ac, T ad,
+        T ba, T bb, T bc, T bd,
+        T ca, T cb, T cc, T cd,
+        T da, T db, T dc, T dd) noexcept
+        : mVals{aa,ab,ac,ad, ba,bb,bc,bd, ca,cb,cc,cd, da,db,dc,dd}
     { }
 
     constexpr MatrixR& operator=(const MatrixR&) noexcept = default;
 
-    auto operator[](size_t idx) noexcept { return al::span<T,4>{&mVals[idx*4], 4}; }
+    constexpr auto operator[](size_t idx) noexcept { return al::span<T,4>{&mVals[idx*4], 4}; }
     constexpr auto operator[](size_t idx) const noexcept
     { return al::span<const T,4>{&mVals[idx*4], 4}; }
 
@@ -106,7 +106,7 @@ public:
 using Matrix = MatrixR<float>;
 
 template<typename T>
-inline VectorR<T> operator*(const MatrixR<T> &mtx, const VectorR<T> &vec) noexcept
+constexpr VectorR<T> operator*(const MatrixR<T> &mtx, const VectorR<T> &vec) noexcept
 {
     return VectorR<T>{
         vec[0]*mtx[0][0] + vec[1]*mtx[1][0] + vec[2]*mtx[2][0] + vec[3]*mtx[3][0],
@@ -115,13 +115,6 @@ inline VectorR<T> operator*(const MatrixR<T> &mtx, const VectorR<T> &vec) noexce
         vec[0]*mtx[0][3] + vec[1]*mtx[1][3] + vec[2]*mtx[2][3] + vec[3]*mtx[3][3]};
 }
 
-template<typename U, typename T>
-inline VectorR<U> cast_to(const VectorR<T> &vec) noexcept
-{
-    return VectorR<U>{static_cast<U>(vec[0]), static_cast<U>(vec[1]),
-        static_cast<U>(vec[2]), static_cast<U>(vec[3])};
-}
-
 } // namespace alu
 
 #endif /* COMMON_VECMAT_H */
-- 
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