From 1f869252379fdc4efdd2e81764edbff5b00b135c Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Mon, 15 Aug 2016 18:45:25 +1000
Subject: [PATCH] matrix: add elementwise sum function overload

---
 matrix.hpp      | 5 +++++
 matrix.ipp      | 7 +++++++
 test/matrix.cpp | 2 ++
 3 files changed, 14 insertions(+)

diff --git a/matrix.hpp b/matrix.hpp
index 09ffd8e1..1bf977a6 100644
--- a/matrix.hpp
+++ b/matrix.hpp
@@ -103,6 +103,11 @@ namespace util {
     matrix<S,T>
     abs (const matrix<S,T>&);
 
+    template <size_t S, typename T>
+    constexpr
+    T
+    sum (const matrix<S,T>&);
+
     template <typename T> using matrix3 = matrix<3,T>;
     template <typename T> using matrix4 = matrix<4,T>;
 
diff --git a/matrix.ipp b/matrix.ipp
index 1bb1e829..770bdce6 100644
--- a/matrix.ipp
+++ b/matrix.ipp
@@ -118,3 +118,10 @@ util::abs (const util::matrix<S,T> &src)
 
 
 ///////////////////////////////////////////////////////////////////////////////
+template <size_t S, typename T>
+constexpr
+T
+util::sum (const util::matrix<S,T> &src)
+{
+    return sum (std::cbegin (src), std::cend (src));
+}
diff --git a/test/matrix.cpp b/test/matrix.cpp
index a12d6fe6..5f32fcfa 100644
--- a/test/matrix.cpp
+++ b/test/matrix.cpp
@@ -11,6 +11,8 @@ main (void)
 {
     util::TAP::logger tap;
 
+    tap.expect_eq (sum (util::matrix4f::IDENTITY), 4.f, "element summation");
+
     {
         // Identity matrix-vector multiplication
         auto v = util::vector4f { 1.f, 2.f, 3.f, 4.f };