From aaa8e75dc125e4116bed76ed14cbfc028bf6e9c7 Mon Sep 17 00:00:00 2001
From: King_DuckZ <king_duckz@gmx.com>
Date: Wed, 1 Feb 2017 01:51:52 +0000
Subject: [PATCH] Implement 2D and 3D cross product.

2D cross product is defined as equivalent to:
res = cross(a.xy0(), b.xy0()).z()
---
 include/vectorwrapper/vectorops.hpp | 18 +++++++++++++++
 test/unit/test_ops.cpp              | 34 ++++++++++++++++++++++++++++-
 2 files changed, 51 insertions(+), 1 deletion(-)

diff --git a/include/vectorwrapper/vectorops.hpp b/include/vectorwrapper/vectorops.hpp
index 1e59495..50c9c60 100644
--- a/include/vectorwrapper/vectorops.hpp
+++ b/include/vectorwrapper/vectorops.hpp
@@ -26,6 +26,11 @@ namespace vwr {
 	template <typename V1, typename V2, size_type S>
 	typename std::common_type<typename Vec<V1>::scalar_type, typename Vec<V2>::scalar_type>::type dot ( const Vec<V1, S>& parLeft, const Vec<V2, S>& parRight );
 
+	template <typename V1, typename V2>
+	typename std::common_type<typename Vec<V1>::scalar_type, typename Vec<V2>::scalar_type>::type cross ( const Vec<V1, 2>& parLeft, const Vec<V2, 2>& parRight );
+	template <typename V1, typename V2>
+	Vec<typename std::common_type<V1, V2>::type> cross ( const Vec<V1, 3>& parLeft, const Vec<V2, 3>& parRight );
+
 	template <typename V1, typename V2, size_type S>
 	inline typename std::common_type<typename Vec<V1>::scalar_type, typename Vec<V2>::scalar_type>::type dot (const Vec<V1, S>& parLeft, const Vec<V2, S>& parRight) {
 		auto retval = parLeft.x() * parRight.x();
@@ -34,6 +39,19 @@ namespace vwr {
 		}
 		return retval;
 	}
+
+	template <typename V1, typename V2>
+	inline typename std::common_type<typename Vec<V1>::scalar_type, typename Vec<V2>::scalar_type>::type cross (const Vec<V1, 2>& parLeft, const Vec<V2, 2>& parRight) {
+		return parLeft.x() * parRight.y() - parLeft.y() * parRight.x();
+	}
+	template <typename V1, typename V2>
+	inline Vec<typename std::common_type<V1, V2>::type> cross (const Vec<V1, 3>& parLeft, const Vec<V2, 3>& parRight) {
+		return Vec<typename std::common_type<V1, V2>::type>(
+			parLeft.y() * parRight.z() - parLeft.z() * parRight.y(),
+			parLeft.z() * parRight.x() - parLeft.x() * parRight.z(),
+			parLeft.x() * parRight.y() - parLeft.y() * parRight.x()
+		);
+	}
 } //namespace vwr
 
 #endif
diff --git a/test/unit/test_ops.cpp b/test/unit/test_ops.cpp
index 157089e..4fa0b85 100644
--- a/test/unit/test_ops.cpp
+++ b/test/unit/test_ops.cpp
@@ -23,7 +23,7 @@ namespace vwr {
 
 typedef vwr::Vec<UnorderedVector> uvec3i;
 
-TEST(vwr, ops) {
+TEST(vwr, dot) {
 	using namespace vwr;
 
 	ivec3 a(1);
@@ -43,3 +43,35 @@ TEST(vwr, ops) {
 	EXPECT_EQ(7*5+2*2+9*8, dot(a, c));
 	EXPECT_EQ(7*6+2*9+9*3, dot(b, c));
 }
+
+TEST(vwr, cross2D) {
+	using namespace vwr;
+
+	ivec2 a(53, 97);
+	ivec2 b(71, -30);
+
+	EXPECT_EQ(-8477, cross(a, b));
+
+	a /= 4;
+	b /= -2;
+	EXPECT_EQ(1035, cross(a, b));
+}
+
+TEST(vwr, cross3D) {
+	using namespace vwr;
+
+	ivec3 a(5, 7, 13);
+	ivec3 b(17, 19, 23);
+
+	ivec3 res(-86, 106, -24);
+	EXPECT_EQ(res, cross(a, b));
+
+	a.x() *= 10;
+	a.y() *= -8;
+	a.z() *= 37;
+	b *= -99;
+	res.x() = 1032273;
+	res.y() = -695673;
+	res.z() = -188298;
+	EXPECT_EQ(res, cross(a, b));
+}