Make swap constexpr.

Morwenn · Morwenn · commit 92fdd0ac0f0c · 2016-05-31T20:58:00.000+02:00
constexpr support for swap, relying on the fact that only built-in
integers are handled. It allows to get rid of the &lt;utility&gt; include too.
diff --git a/include/cpp-gray/gray.h b/include/cpp-gray/gray.h
@@ -30,7 +30,6 @@
 #include <cstddef>
 #include <limits>
 #include <type_traits>
-#include <utility>
 
 namespace cppgray
 {
@@ -253,7 +252,7 @@ namespace cppgray
     // Utility functions
 
     template<typename Unsigned>
-    auto swap(gray_code<Unsigned>& lhs, gray_code<Unsigned>& rhs) noexcept
+    constexpr auto swap(gray_code<Unsigned>& lhs, gray_code<Unsigned>& rhs) noexcept
         -> void;
 
     ////////////////////////////////////////////////////////////
diff --git a/include/cpp-gray/gray.inl b/include/cpp-gray/gray.inl
@@ -416,11 +416,12 @@ constexpr auto operator^=(Unsigned& lhs, gray_code<Unsigned> rhs) noexcept
 // Utility functions
 
 template<typename Unsigned>
-auto swap(gray_code<Unsigned>& lhs, gray_code<Unsigned>& rhs) noexcept
+constexpr auto swap(gray_code<Unsigned>& lhs, gray_code<Unsigned>& rhs) noexcept
     -> void
 {
-    using std::swap;
-    swap(lhs.value, rhs.value);
+    auto tmp = lhs.value;
+    lhs.value = rhs.value;
+    rhs.value = tmp;
 }
 
 ////////////////////////////////////////////////////////////

Original file line number	Diff line number	Diff line change
`@@ -416,11 +416,12 @@ constexpr auto operator^=(Unsigned& lhs, gray_code<Unsigned> rhs) noexcept`
`416`	`416`	`// Utility functions`
`417`	`417`
`418`	`418`	`template<typename Unsigned>`
`419`		`-auto swap(gray_code<Unsigned>& lhs, gray_code<Unsigned>& rhs) noexcept`
	`419`	`+constexpr auto swap(gray_code<Unsigned>& lhs, gray_code<Unsigned>& rhs) noexcept`
`420`	`420`	`-> void`
`421`	`421`	`{`
`422`		`- using std::swap;`
`423`		`- swap(lhs.value, rhs.value);`
	`422`	`+ auto tmp = lhs.value;`
	`423`	`+ lhs.value = rhs.value;`
	`424`	`+ rhs.value = tmp;`
`424`	`425`	`}`
`425`	`426`
`426`	`427`	`////////////////////////////////////////////////////////////`