From 64dd72db85279a822df1dadf002fbe2ad4e586c5 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Fri, 20 Apr 2012 18:02:54 +1000
Subject: [PATCH] Add support for differing types in almost_equal

---
 maths.hpp | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/maths.hpp b/maths.hpp
index 1ff22c54..5d83533f 100644
--- a/maths.hpp
+++ b/maths.hpp
@@ -22,6 +22,7 @@
 
 #include "annotations.hpp"
 
+#include <type_traits>
 
 template <typename T>
 T 
@@ -62,13 +63,24 @@ almost_equal (const T &a, const T &b)
 
 
 template <typename Ta, typename Tb>
-bool
+typename std::enable_if<
+    std::is_arithmetic<Ta>::value && std::is_arithmetic<Tb>::value,
+    bool
+>::type
 almost_equal (const Ta &a, const Tb &b) {
     return almost_equal <decltype(a + b)> (static_cast<decltype(a + b)>(a),
                                            static_cast<decltype(a + b)>(b));
 }
 
 
+template <typename Ta, typename Tb>
+typename std::enable_if<
+    !std::is_arithmetic<Ta>::value || !std::is_arithmetic<Tb>::value,
+    bool
+>::type
+almost_equal (const Ta &a, const Tb &b)
+    { return a == b; }
+
 const double PI = 3.141592653589793238462643;
 
 inline double