Add support for comparison of Approx with strong typedefs

closes catchorg#652
jbcoe · Oct 4, 2016 · 0f098bd · 0f098bd
1 parent 88732e8
commit 0f098bd
Show file tree

Hide file tree

Showing 2 changed files with 43 additions and 0 deletions.
diff --git a/include/internal/catch_approx.hpp b/include/internal/catch_approx.hpp
@@ -13,6 +13,10 @@
 #include <cmath>
 #include <limits>
 
+#if defined(__cplusplus) && __cplusplus >= 201103L
+#include <type_traits>
+#endif
+
 namespace Catch {
 namespace Detail {
 
@@ -40,7 +44,19 @@ namespace Detail {
             approx.scale( m_scale );
             return approx;
         }
+#if defined(__cplusplus) && __cplusplus >= 201103L
+        template <typename T, typename = typename std::enable_if<std::is_constructible<T, double>::value>::type>
+        friend bool operator == ( const T& lhs, Approx const& rhs ) {
+            // Thanks to Richard Harris for his help refining this formula
+            auto lhs_v = (double)lhs;
+            return fabs( lhs_v - rhs.m_value ) < rhs.m_epsilon * (rhs.m_scale + (std::max)( fabs(lhs_v), fabs(rhs.m_value) ) );
+        }
 
+        template <typename T, typename = typename std::enable_if<std::is_constructible<T, double>::value>::type>
+        friend bool operator == ( Approx const& lhs, const T& rhs ) {
+            return operator==( rhs, lhs );
+        }
+#else  // defined(__cplusplus) && __cplusplus >= 201103L
         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) ) );
@@ -49,6 +65,7 @@ namespace Detail {
         friend bool operator == ( Approx const& lhs, double rhs ) {
             return operator==( rhs, lhs );
         }
+#endif  // defined(__cplusplus) && __cplusplus >= 201103L
 
         friend bool operator != ( double lhs, Approx const& rhs ) {
             return !operator==( lhs, rhs );

diff --git a/projects/SelfTest/ApproxTests.cpp b/projects/SelfTest/ApproxTests.cpp
@@ -110,3 +110,29 @@ TEST_CASE( "Approximate PI", "[Approx][PI]" )
     REQUIRE( divide( 22, 7 ) == Approx( 3.141 ).epsilon( 0.001 ) );
     REQUIRE( divide( 22, 7 ) != Approx( 3.141 ).epsilon( 0.0001 ) );
 }
+
+////////////////////////////////////////////////////////////////////////////////
+
+#if defined(__cplusplus) && __cplusplus >= 201103L
+class StrongDoubleTypedef
+{
+  double d_ = 0.0;
+
+  public:
+    explicit StrongDoubleTypedef(double d) : d_(d) {}
+    explicit operator double() const { return d_; }
+};
+
+TEST_CASE
+(
+ "Comparison with explicitly convertible types",
+ "[Approx]"
+)
+{
+  StrongDoubleTypedef td(10.0);
+
+  REQUIRE(td == Approx(10.0));
+}
+#endif // defined(__cplusplus) && __cplusplus >= 201103L
+
+////////////////////////////////////////////////////////////////////////////////