From ef76246a9afc12c735ea8e0317d45b9c474a3e5a Mon Sep 17 00:00:00 2001
From: Stanislaw Halik <sthalik@misaki.pl>
Date: Wed, 12 Apr 2017 01:38:59 +0200
Subject: compat/simple-mat: simplify SFINAE

variable templates rock ass.
---
 compat/simple-mat.hpp | 284 +++++++++++++++++++++++++-------------------------
 1 file changed, 144 insertions(+), 140 deletions(-)

diff --git a/compat/simple-mat.hpp b/compat/simple-mat.hpp
index 906c0969..1146984a 100644
--- a/compat/simple-mat.hpp
+++ b/compat/simple-mat.hpp
@@ -8,127 +8,117 @@
 
 #pragma once
 
+#include <cmath>
 #include "export.hpp"
+#include <compat/util.hpp>
 
 #include <initializer_list>
 #include <type_traits>
 #include <utility>
 
-namespace {
-    // last param to fool SFINAE into overloading
-    template<int i, int j, int>
-    struct equals
-    {
-        enum { value = i == j };
-    };
-    template<int i, int j, int min>
-    struct maybe_add_swizzle
-    {
-        enum { value = (i == 1 || j == 1) && (i >= min || j >= min) };
-    };
-    template<int i1, int j1, int i2, int j2>
-    struct is_vector_pair
-    {
-        enum { value = (i1 == i2 && j1 == 1 && j2 == 1) || (j1 == j2 && i1 == 1 && i2 == 1) };
-    };
-    template<int i, int j>
-    struct vector_len
-    {
-        enum { value = i > j ? i : j };
-    };
-    template<int a, int b, int c, int d>
-    struct is_dim3
-    {
-        enum { value = (a == 1 && c == 1 && b == 3 && d == 3) || (a == 3 && c == 3 && b == 1 && d == 1) };
-        enum { P = a == 1 ? 1 : 3 };
-        enum { Q = a == 1 ? 3 : 1 };
-    };
+namespace mat_detail {
 
-    template<typename num, int h, int w, typename...ts>
-    struct is_arglist_correct
-    {
-        enum { value = h * w == sizeof...(ts) };
-    };
-}
+// `zz' param to fool into SFINAE member overload
 
-template<typename num, int h_, int w_>
-class Mat
-{
-    static_assert(h_ > 0 && w_ > 0, "must have positive mat dimensions");
-    num data[h_][w_];
+template<int i, int j, int k, int zz>
+constexpr bool equals = ((void)zz, i == k && j != k);
 
-public:
-    template<int Q = w_> typename std::enable_if<equals<Q, 1, 0>::value, num>::type
-    inline operator()(int i) const { return data[i][0]; }
+template<int i, int j, int min>
+constexpr bool maybe_swizzle =
+        (i == 1 || j == 1) && (i >= min || j >= min);
 
-    template<int P = h_> typename std::enable_if<equals<P, 1, 1>::value, num>::type
-    inline operator()(int i) const { return data[0][i]; }
+template<int i1, int j1, int i2, int j2>
+constexpr bool is_vector_pair =
+        (i1 == i2 && j1 == 1 && j2 == 1) || (j1 == j2 && i1 == 1 && i2 == 1);
 
-    template<int Q = w_> typename std::enable_if<equals<Q, 1, 2>::value, num&>::type
-    inline operator()(int i) { return data[i][0]; }
+template<int i, int j>
+constexpr unsigned vector_len = i > j ? i : j;
 
-    template<int P = h_> typename std::enable_if<equals<P, 1, 3>::value, num&>::type
-    inline operator()(int i) { return data[0][i]; }
+template<int a, int b, int c, int d>
+constexpr bool dim3 =
+        (a == 3 || b == 3) && (c == 3 || d == 3) &&
+        (a == 1 || b == 1) && (c == 1 || d == 1);
 
-    template<int Q = w_> typename std::enable_if<equals<Q, 1, 0>::value, num>::type
-    inline operator()(unsigned i) const { return data[i][0]; }
+template<int h, int w, typename... ts>
+constexpr bool arglist_correct = h * w == sizeof...(ts);
 
-    template<int P = h_> typename std::enable_if<equals<P, 1, 1>::value, num>::type
-    inline operator()(unsigned i) const { return data[0][i]; }
+template<bool x, typename t>
+using sfinae = typename std::enable_if<x, t>::type;
 
-    template<int Q = w_> typename std::enable_if<equals<Q, 1, 2>::value, num&>::type
-    inline operator()(unsigned i) { return data[i][0]; }
+template<typename num, int h_, int w_>
+class Mat
+{
+    static_assert(h_ > 0 && w_ > 0, "must have positive mat dimensions");
+    num data[h_][w_];
 
-    template<int P = h_> typename std::enable_if<equals<P, 1, 3>::value, num&>::type
-    inline operator()(unsigned i) { return data[0][i]; }
+#define OTR_ASSERT_SWIZZLE static_assert(P == h_ && Q == w_, "")
 
-#define OPENTRACK_ASSERT_SWIZZLE static_assert(P == h_ && Q == w_, "")
+    Mat(std::initializer_list<num>&& init)
+    {
+        auto iter = init.begin();
+        for (int j = 0; j < h_; j++)
+            for (int i = 0; i < w_; i++)
+                data[j][i] = *iter++;
+    }
+
+public:
+    // start sfinae-R-us block
 
-    template<int P = h_, int Q = w_> typename std::enable_if<maybe_add_swizzle<P, Q, 1>::value, num>::type
-    x() const { OPENTRACK_ASSERT_SWIZZLE; return operator()(0); }
+    // rebinding w_ and h_ since SFINAE requires dependent variables
 
-    template<int P = h_, int Q = w_> typename std::enable_if<maybe_add_swizzle<P, Q, 2>::value, num>::type
-    y() const { OPENTRACK_ASSERT_SWIZZLE; return operator()(1); }
+    template<int P = h_, int Q = w_> sfinae<equals<Q, P, 1, 0>, num>
+    OTR_FLATTEN operator()(int i) const { OTR_ASSERT_SWIZZLE; return data[i][0]; }
+    template<int P = h_, int Q = w_> sfinae<equals<Q, 0, 1, 0>, num&>
+    OTR_FLATTEN operator()(int i) { OTR_ASSERT_SWIZZLE; return data[i][0]; }
 
-    template<int P = h_, int Q = w_> typename std::enable_if<maybe_add_swizzle<P, Q, 3>::value, num>::type
-    z() const { OPENTRACK_ASSERT_SWIZZLE; return operator()(2); }
+    template<int P = h_, int Q = w_> sfinae<equals<P, Q, 1, 1>, num>
+    OTR_FLATTEN operator()(int i) const { OTR_ASSERT_SWIZZLE; return data[0][i]; }
+    template<int P = h_, int Q = w_> sfinae<equals<P, Q, 1, 1>, num&>
+    OTR_FLATTEN operator()(int i) { OTR_ASSERT_SWIZZLE; return data[0][i]; }
 
-    template<int P = h_, int Q = w_> typename std::enable_if<maybe_add_swizzle<P, Q, 4>::value, num>::type
-    w() const { OPENTRACK_ASSERT_SWIZZLE; return operator()(3); }
+    template<int P = h_, int Q = w_> sfinae<maybe_swizzle<P, Q, 1>, num>
+    OTR_FLATTEN x() const { OTR_ASSERT_SWIZZLE; return operator()(0); }
+    template<int P = h_, int Q = w_> sfinae<maybe_swizzle<P, Q, 1>, num&>
+    OTR_FLATTEN x() { OTR_ASSERT_SWIZZLE; return operator()(0); }
 
-    template<int P = h_, int Q = w_> typename std::enable_if<maybe_add_swizzle<P, Q, 1>::value, num&>::type
-    x() { OPENTRACK_ASSERT_SWIZZLE; return operator()(0); }
+    template<int P = h_, int Q = w_> sfinae<maybe_swizzle<P, Q, 2>, num>
+    OTR_FLATTEN y() const { OTR_ASSERT_SWIZZLE; return operator()(1); }
+    template<int P = h_, int Q = w_> sfinae<maybe_swizzle<P, Q, 2>, num&>
+    OTR_FLATTEN y() { OTR_ASSERT_SWIZZLE; return operator()(1); }
 
-    template<int P = h_, int Q = w_> typename std::enable_if<maybe_add_swizzle<P, Q, 2>::value, num&>::type
-    y() { OPENTRACK_ASSERT_SWIZZLE; return operator()(1); }
+    template<int P = h_, int Q = w_> sfinae<maybe_swizzle<P, Q, 3>, num>
+    OTR_FLATTEN z() const { OTR_ASSERT_SWIZZLE; return operator()(2); }
+    template<int P = h_, int Q = w_> sfinae<maybe_swizzle<P, Q, 3>, num&>
+    OTR_FLATTEN z() { OTR_ASSERT_SWIZZLE; return operator()(2); }
 
-    template<int P = h_, int Q = w_> typename std::enable_if<maybe_add_swizzle<P, Q, 3>::value, num&>::type
-    z() { OPENTRACK_ASSERT_SWIZZLE; return operator()(2); }
+    template<int P = h_, int Q = w_> sfinae<maybe_swizzle<P, Q, 4>, num>
+    OTR_FLATTEN w() const { OTR_ASSERT_SWIZZLE; return operator()(3); }
+    template<int P = h_, int Q = w_> sfinae<maybe_swizzle<P, Q, 4>, num&>
+    OTR_FLATTEN w() { OTR_ASSERT_SWIZZLE; return operator()(3); }
+
+    // end sfinae-R-us block
 
-    template<int P = h_, int Q = w_> typename std::enable_if<maybe_add_swizzle<P, Q, 4>::value, num&>::type
-    w() { OPENTRACK_ASSERT_SWIZZLE; return operator()(3); }
     // parameters w_ and h_ are rebound so that SFINAE occurs
     // removing them causes a compile-time error -sh 20150811
 
     template<int R, int S, int P = h_, int Q = w_>
-    typename std::enable_if<is_vector_pair<R, S, P, Q>::value, num>::type
+    sfinae<is_vector_pair<R, S, P, Q>, num>
     dot(const Mat<num, R, S>& p2) const
     {
-        static_assert(P == h_ && Q == w_, "");
+        OTR_ASSERT_SWIZZLE;
 
         num ret = 0;
-        constexpr int len = vector_len<R, S>::value;
-        for (int i = 0; i < len; i++)
+        static constexpr unsigned len = vector_len<R, S>;
+        for (unsigned i = 0; i < len; i++)
             ret += operator()(i) * p2(i);
         return ret;
     }
 
-    template<int R, int S, int P = h_, int Q = w_>
-    typename std::enable_if<is_dim3<P, Q, R, S>::value, Mat<num, is_dim3<P, Q, R, S>::P, is_dim3<P, Q, R, S>::Q>>::type
+    template<int R, int S, int P = h_, int Q = w_> sfinae<dim3<P, Q, R, S>, Mat<num, 3, 1>>
     cross(const Mat<num, R, S>& p2) const
     {
-        static_assert(P == h_ && Q == w_, "");
-        decltype(*this)& p1 = *this;
+        OTR_ASSERT_SWIZZLE;
+        decltype(*this)& OTR_RESTRICT p1 = *this;
 
         return Mat<num, R, S>(p1.y() * p2.z() - p2.y() * p1.z(),
                               p2.x() * p1.z() - p1.x() * p2.z(),
@@ -153,24 +143,6 @@ public:
         return ret;
     }
 
-    Mat<num, h_, w_> operator+(const num& other) const
-    {
-        Mat<num, h_, w_> ret;
-        for (int j = 0; j < h_; j++)
-            for (int i = 0; i < w_; i++)
-                ret(j, i) = data[j][i] + other;
-        return ret;
-    }
-
-    Mat<num, h_, w_> operator-(const num& other) const
-    {
-        Mat<num, h_, w_> ret;
-        for (int j = 0; j < h_; j++)
-            for (int i = 0; i < w_; i++)
-                ret(j, i) = data[j][i] - other;
-        return ret;
-    }
-
     template<int p>
     Mat<num, h_, p> operator*(const Mat<num, w_, p>& other) const
     {
@@ -191,11 +163,12 @@ public:
     inline num operator()(unsigned j, unsigned i) const { return data[j][i]; }
     inline num& operator()(unsigned j, unsigned i) { return data[j][i]; }
 
-    template<typename... ts, int h__ = h_, int w__ = w_,
-             typename = typename std::enable_if<is_arglist_correct<num, h__, w__, ts...>::value>::type>
+    template<typename... ts, int P = h_, int Q = w_,
+             typename = sfinae<arglist_correct<P, Q, ts...>, void>>
     Mat(const ts... xs)
     {
-        static_assert(h__ == h_ && w__ == w_, "");
+        OTR_ASSERT_SWIZZLE;
+        static_assert(arglist_correct<P, Q, ts...>, "");
 
         std::initializer_list<num> init = { static_cast<num>(xs)... };
 
@@ -209,38 +182,31 @@ public:
                 data[j][i] = num(0);
     }
 
-    Mat(const num* mem)
+    Mat(const num* OTR_RESTRICT mem)
     {
         for (int j = 0; j < h_; j++)
             for (int i = 0; i < w_; i++)
                 data[j][i] = mem[i*h_+j];
     }
 
-    Mat(std::initializer_list<num>&& init)
-    {
-        auto iter = init.begin();
-        for (int j = 0; j < h_; j++)
-            for (int i = 0; i < w_; i++)
-                data[j][i] = *iter++;
-    }
-
-    operator num*() { return reinterpret_cast<num*>(data); }
-    operator const num*() const { return reinterpret_cast<const num*>(data); }
+    OTR_ALWAYS_INLINE operator num*() { return reinterpret_cast<num*>(data); }
+    OTR_ALWAYS_INLINE operator const num*() const { return reinterpret_cast<const num*>(data); }
 
     // XXX add more operators as needed, third-party dependencies mostly
     // not needed merely for matrix algebra -sh 20141030
 
-    template<int h__ = h_>
-    static typename std::enable_if<h_ == w_, Mat<num, h__, h__>>::type eye()
+    template<int P = h_>
+    static typename std::enable_if<P == w_, Mat<num, P, P>>::type eye()
     {
-        static_assert(h_ == h__, "");
+        static_assert(P == h_, "");
 
-        Mat<num, h_, h_> ret;
-        for (int j = 0; j < h_; j++)
+        Mat<num, P, P> ret;
+
+        for (int j = 0; j < P; j++)
             for (int i = 0; i < w_; i++)
                 ret.data[j][i] = 0;
 
-        for (int i = 0; i < h_; i++)
+        for (int i = 0; i < P; i++)
             ret.data[i][i] = 1;
 
         return ret;
@@ -258,22 +224,6 @@ public:
     }
 };
 
-template<typename num, int h, int w>
-Mat<num, h, w> operator*(num scalar, const Mat<num, h, w>& mat)
-{
-    return mat * scalar;
-}
-
-template<typename num, int h_, int w_>
-Mat<num, h_, w_> operator*(const Mat<num, h_, w_>& self, num other)
-{
-    Mat<num, h_, w_> ret;
-    for (int j = 0; j < h_; j++)
-        for (int i = 0; i < w_; i++)
-            ret(j, i) = self(j, i) * other;
-    return ret;
-}
-
 template<typename num>
 class Quat : Mat<num, 4, 1>
 {
@@ -287,7 +237,7 @@ class Quat : Mat<num, 4, 1>
     }
 
     inline num elt(idx k) const { return operator()(k); }
-    inline num& elt(idx k) { return operator()(k); }
+    inline num& elt(idx k) { return Mat<num, 4, 1>::operator()(int(k)); }
 public:
     Quat(num w, num x, num y, num z) : Mat<num, 4, 1>(w, x, y, z)
     {
@@ -320,12 +270,11 @@ public:
     {
         const quat& OTR_RESTRICT q1 = *this;
         return quat(-q1.x() * q2.x() - q1.y() * q2.y() - q1.z() * q2.z() + q1.w() * q2.w(),
-                     q1.x() * q2.w() + q1.y() * q2.z() - q1.z() * q2.y() + q1.w() * q2.x(),
+                    q1.x() * q2.w() + q1.y() * q2.z() - q1.z() * q2.y() + q1.w() * q2.x(),
                     -q1.x() * q2.z() + q1.y() * q2.w() + q1.z() * q2.x() + q1.w() * q2.y(),
-                     q1.x() * q2.y() - q1.y() * q2.x() + q1.z() * q2.w() + q1.w() * q2.z());
+                    q1.x() * q2.y() - q1.y() * q2.x() + q1.z() * q2.w() + q1.w() * q2.z());
     }
 
-
     inline num w() const { return elt(qw); }
     inline num x() const { return elt(qx); }
     inline num y() const { return elt(qy); }
@@ -336,3 +285,58 @@ public:
     inline num& y() { return elt(qy); }
     inline num& z() { return elt(qz); }
 };
+
+} // ns detail
+
+template<typename num, int h, int w>
+using Mat = mat_detail::Mat<num, h, w>;
+
+template<typename num, int h, int w>
+inline Mat<num, h, w> operator*(num scalar, const Mat<num, h, w>& mat) { return mat * scalar; }
+
+template<typename num, int h, int w>
+inline Mat<num, h, w> operator-(num scalar, const Mat<num, h, w>& mat) { return mat - scalar; }
+
+template<typename num, int h, int w>
+inline Mat<num, h, w> operator+(num scalar, const Mat<num, h, w>& mat) { return mat + scalar; }
+
+template<typename num, int h_, int w_>
+inline Mat<num, h_, w_> operator*(const Mat<num, h_, w_>& OTR_RESTRICT self, num other)
+{
+    Mat<num, h_, w_> ret;
+    for (int j = 0; j < h_; j++)
+        for (int i = 0; i < w_; i++)
+            ret(j, i) = self(j, i) * other;
+    return ret;
+}
+
+template<typename num, int h_, int w_>
+inline Mat<num, h_, w_> operator-(const Mat<num, h_, w_>& OTR_RESTRICT self, num other)
+{
+    Mat<num, h_, w_> ret;
+    for (int j = 0; j < h_; j++)
+        for (int i = 0; i < w_; i++)
+            ret(j, i) = self(j, i) - other;
+    return ret;
+}
+
+template<typename num, int h_, int w_>
+inline Mat<num, h_, w_> operator+(const Mat<num, h_, w_>& OTR_RESTRICT self, num other)
+{
+    Mat<num, h_, w_> ret;
+    for (int j = 0; j < h_; j++)
+        for (int i = 0; i < w_; i++)
+            ret(j, i) = self(j, i) + other;
+    return ret;
+}
+
+template<typename num>
+using Quat_ = mat_detail::Quat<num>;
+
+using Quat = Quat_<double>;
+
+template class mat_detail::Mat<float, 3, 3>;
+template class mat_detail::Mat<float, 6, 1>;
+template class mat_detail::Mat<float, 3, 1>;
+
+// eof
-- 
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