From 3a4b7114676488fc69dd99a69243f6782cb877f9 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Tue, 18 Oct 2016 16:45:38 +1100
Subject: [PATCH] quaternion: add assignment-multiply operator

---
 quaternion.cpp | 12 +++++++++++-
 quaternion.hpp |  5 +++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/quaternion.cpp b/quaternion.cpp
index 7f956afe..ebeaf5a7 100644
--- a/quaternion.cpp
+++ b/quaternion.cpp
@@ -127,6 +127,15 @@ util::operator* (const quaternion<T> a, const quaternion<T> b)
 }
 
 
+//-----------------------------------------------------------------------------
+template <typename T>
+quaternion<T>&
+util::operator*= (quaternion<T> &a, const quaternion<T> b)
+{
+    return a = a * b;
+}
+
+
 //-----------------------------------------------------------------------------
 template <typename T>
 quaternion<T>
@@ -251,9 +260,10 @@ namespace util::debug {
 
 ///////////////////////////////////////////////////////////////////////////////
 #define INSTANTIATE(T)                                                          \
-template util::vector3<T> util::rotate (util::vector3<T>, util::quaternion<T>);   \
+template util::vector3<T> util::rotate (util::vector3<T>, util::quaternion<T>); \
 template quaternion<T> util::conjugate (quaternion<T>);                         \
 template quaternion<T> util::operator* (quaternion<T>, quaternion<T>);          \
+template quaternion<T>& util::operator*= (quaternion<T>&, quaternion<T>);       \
 template quaternion<T> util::operator/ (quaternion<T>, quaternion<T>);          \
 template bool util::almost_equal (util::quaternion<T>, util::quaternion<T>);    \
 template std::ostream& util::operator<< (std::ostream&, quaternion<T>);         \
diff --git a/quaternion.hpp b/quaternion.hpp
index 362313a3..d1897ea8 100644
--- a/quaternion.hpp
+++ b/quaternion.hpp
@@ -89,6 +89,11 @@ namespace util {
     quaternion<T>
     operator* (quaternion<T>, quaternion<T>);
 
+    //-------------------------------------------------------------------------
+    template <typename T>
+    quaternion<T>&
+    operator*= (quaternion<T>&, quaternion<T>);
+
     //-------------------------------------------------------------------------
     template <typename T>
     quaternion<T>