From 67535647999faea49daf43bfeafeb4c4fc4f26ea Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Fri, 5 Mar 2021 19:39:40 +0000
Subject: Template rotations and add one for 2D rotation matrix

---
 lib/maths.cpp       | 18 +++++++++++++-----
 lib/maths.h         |  1 +
 test/test-maths.cpp |  1 +
 3 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/lib/maths.cpp b/lib/maths.cpp
index 5800b1b..4ae0693 100644
--- a/lib/maths.cpp
+++ b/lib/maths.cpp
@@ -24,35 +24,43 @@ operator^(M & m, glm::ivec2 xy)
 }
 
 // Create a matrix for the angle, given the targets into the matrix
+template<typename M>
 inline auto
-rotation(float a, glm::ivec2 c1, glm::ivec2 s1, glm::ivec2 c2, glm::ivec2 ms2)
+rotation(typename M::value_type a, glm::ivec2 c1, glm::ivec2 s1, glm::ivec2 c2, glm::ivec2 ms2)
 {
-	glm::mat4 m(1);
+	M m(1);
 	sincosf(a, m ^ s1, m ^ c1);
 	m ^ c2 = m ^ c1;
 	m ^ ms2 = -(m ^ s1);
 	return m;
 }
 
+// Create a flat (2D) transformation matrix
+glm::mat2
+rotate_flat(float a)
+{
+	return rotation<glm::mat2>(a, {0, 0}, {0, 1}, {1, 1}, {1, 0});
+}
+
 // Create a roll transformation matrix
 glm::mat4
 rotate_roll(float a)
 {
-	return rotation(a, {0, 0}, {0, 1}, {1, 1}, {1, 0});
+	return rotation<glm::mat4>(a, {0, 0}, {0, 1}, {1, 1}, {1, 0});
 }
 
 // Create a yaw transformation matrix
 glm::mat4
 rotate_yaw(float a)
 {
-	return rotation(a, {0, 0}, {2, 0}, {2, 2}, {0, 2});
+	return rotation<glm::mat4>(a, {0, 0}, {2, 0}, {2, 2}, {0, 2});
 }
 
 // Create a pitch transformation matrix
 glm::mat4
 rotate_pitch(float a)
 {
-	return rotation(a, {1, 1}, {1, 2}, {2, 2}, {2, 1});
+	return rotation<glm::mat4>(a, {1, 1}, {1, 2}, {2, 2}, {2, 1});
 }
 
 // Create a bomcined yaw, pitch, roll transformation matrix
diff --git a/lib/maths.h b/lib/maths.h
index a3a391d..dc0c617 100644
--- a/lib/maths.h
+++ b/lib/maths.h
@@ -45,6 +45,7 @@ sincosf(float a)
 	return sc;
 }
 
+glm::mat2 rotate_flat(float);
 glm::mat4 rotate_roll(float);
 glm::mat4 rotate_yaw(float);
 glm::mat4 rotate_pitch(float);
diff --git a/test/test-maths.cpp b/test/test-maths.cpp
index ea60f2a..420b69e 100644
--- a/test/test-maths.cpp
+++ b/test/test-maths.cpp
@@ -5,6 +5,7 @@
 #include <glm/gtx/transform.hpp>
 #include <stream_support.hpp>
 #include <string_view>
+#include <type_traits>
 
 #include <glm/glm.hpp>
 #include <maths.h>
-- 
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