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diff --git a/include/internal/catch_approx.hpp b/include/internal/catch_approx.hpp
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+++ b/include/internal/catch_approx.hpp
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+/*
+ *  Created by Phil on 28/04/2011.
+ *  Copyright 2010 Two Blue Cubes Ltd. All rights reserved.
+ *
+ *  Distributed under the Boost Software License, Version 1.0. (See accompanying
+ *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+ */
+#ifndef TWOBLUECUBES_CATCH_APPROX_HPP_INCLUDED
+#define TWOBLUECUBES_CATCH_APPROX_HPP_INCLUDED
+
+#include "catch_tostring.h"
+
+#include <cmath>
+#include <limits>
+
+namespace Catch {
+namespace Detail {
+
+    class Approx {
+    public:
+        explicit Approx ( double value )
+        :   m_epsilon( std::numeric_limits<float>::epsilon()*100 ),
+            m_scale( 1.0 ),
+            m_value( value )
+        {}
+
+        Approx( Approx const& other )
+        :   m_epsilon( other.m_epsilon ),
+            m_scale( other.m_scale ),
+            m_value( other.m_value )
+        {}
+
+        static Approx custom() {
+            return Approx( 0 );
+        }
+
+        Approx operator()( double value ) {
+            Approx approx( value );
+            approx.epsilon( m_epsilon );
+            approx.scale( m_scale );
+            return approx;
+        }
+
+        friend bool operator == ( double lhs, Approx const& rhs ) {
+            // Thanks to Richard Harris for his help refining this formula
+            return fabs( lhs - rhs.m_value ) < rhs.m_epsilon * (rhs.m_scale + (std::max)( fabs(lhs), fabs(rhs.m_value) ) );
+        }
+
+        friend bool operator == ( Approx const& lhs, double rhs ) {
+            return operator==( rhs, lhs );
+        }
+
+        friend bool operator != ( double lhs, Approx const& rhs ) {
+            return !operator==( lhs, rhs );
+        }
+
+        friend bool operator != ( Approx const& lhs, double rhs ) {
+            return !operator==( rhs, lhs );
+        }
+
+        Approx& epsilon( double newEpsilon ) {
+            m_epsilon = newEpsilon;
+            return *this;
+        }
+
+        Approx& scale( double newScale ) {
+            m_scale = newScale;
+            return *this;
+        }
+
+        std::string toString() const {
+            std::ostringstream oss;
+            oss << "Approx( " << Catch::toString( m_value ) << " )";
+            return oss.str();
+        }
+
+    private:
+        double m_epsilon;
+        double m_scale;
+        double m_value;
+    };
+}
+
+template<>
+inline std::string toString<Detail::Approx>( Detail::Approx const& value ) {
+    return value.toString();
+}
+
+} // end namespace Catch
+
+#endif // TWOBLUECUBES_CATCH_APPROX_HPP_INCLUDED