From cee9951f826c2d95c103f04d47d6a688277183e0 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Wed, 28 Jan 2015 15:00:20 +1100
Subject: [PATCH] vector: add difference(2) methods

---
 vector.cpp | 20 ++++++++++++++++++++
 vector.hpp |  3 +++
 2 files changed, 23 insertions(+)

diff --git a/vector.cpp b/vector.cpp
index 2c1c5a03..875d841a 100644
--- a/vector.cpp
+++ b/vector.cpp
@@ -241,6 +241,26 @@ util::vector<S,T>::magnitude2 (void) const {
 }
 
 
+//-----------------------------------------------------------------------------
+template <size_t S, typename T>
+T
+util::vector<S,T>::difference (const util::vector<S,T> &rhs) const {
+    // TODO: change the signature to ensure it does not truncate
+    return static_cast<T> (std::sqrt (difference2 (rhs)));
+}
+
+
+//-----------------------------------------------------------------------------
+template <size_t S, typename T>
+T
+util::vector<S,T>::difference2 (const util::vector<S,T> &rhs) const {
+    T sum {0};
+    for (size_t i = 0; i < S; ++i)
+        sum += pow2 (this->data[i] - rhs.data[i]);
+    return sum;
+}
+
+//-----------------------------------------------------------------------------
 template <size_t S, typename T>
 util::vector<S,T>&
 util::vector<S,T>::normalise (void) {
diff --git a/vector.hpp b/vector.hpp
index 95b6ccb5..2b827806 100644
--- a/vector.hpp
+++ b/vector.hpp
@@ -67,6 +67,9 @@ namespace util {
         T magnitude  (void) const;
         T magnitude2 (void) const;
 
+        T difference  (const vector<S,T>&) const;
+        T difference2 (const vector<S,T>&) const;
+
         T dot (const vector<S,T>&) const;
 
         vector<S,T>& normalise  (void);