From d63c9803da102dcf87979319d6cf366ef38d5bb0 Mon Sep 17 00:00:00 2001
From: Neil MacIntosh <neilmac@microsoft.com>
Date: Sun, 29 May 2016 14:05:09 -0700
Subject: [PATCH] Added comparison operators.

---
 include/span.h       | 20 ++++++++++++--------
 tests/span_tests.cpp | 28 ++++++++++++++++++----------
 2 files changed, 30 insertions(+), 18 deletions(-)

diff --git a/include/span.h b/include/span.h
index 187f948..2760121 100644
--- a/include/span.h
+++ b/include/span.h
@@ -481,26 +481,30 @@ private:
 };
 
 
-#if 0 // TODO
 // [span.comparison], span comparison operators 
 template <class ElementType, ptrdiff_t Extent>
-constexpr bool operator==(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r) const noexcept;
+constexpr bool operator==(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r) noexcept
+{ return std::equal(l.begin(), l.end(), r.begin(), r.end()); }
 
 template <class ElementType, ptrdiff_t Extent>
-constexpr bool operator!=(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r) const noexcept;
+constexpr bool operator!=(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r) noexcept
+{ return !(l == r); }
 
 template <class ElementType, ptrdiff_t Extent>
-constexpr bool operator<(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r) const noexcept;
+constexpr bool operator<(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r) noexcept
+{ return std::lexicographical_compare(l.begin(), l.end(), r.begin(), r.end()); }
 
 template <class ElementType, ptrdiff_t Extent>
-constexpr bool operator<=(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r) const noexcept;
+constexpr bool operator<=(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r) noexcept
+{ return !(l > r); }
 
 template <class ElementType, ptrdiff_t Extent>
-constexpr bool operator>(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r) const noexcept;
+constexpr bool operator>(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r) noexcept
+{ return r < l; }
 
 template <class ElementType, ptrdiff_t Extent>
-constexpr bool operator>=(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r) const noexcept;
-#endif
+constexpr bool operator>=(const span<ElementType, Extent>& l, const span<ElementType, Extent>& r) noexcept
+{ return !(l < r); }
 
 
 #if 0 // TODO
diff --git a/tests/span_tests.cpp b/tests/span_tests.cpp
index 74182de..694d9a2 100644
--- a/tests/span_tests.cpp
+++ b/tests/span_tests.cpp
@@ -801,23 +801,30 @@ SUITE(span_tests)
         }
     }
 
-#if 0
     TEST(comparison_operators)
     {
         {
-            int arr[10][2];
-            auto s1 = as_span(arr);
-            span<const int, dynamic_range, 2> s2 = s1;
-
+            span<int> s1 = nullptr;
+            span<int> s2 = nullptr;
             CHECK(s1 == s2);
-
-            span<int, 20> s3 = as_span(s1, dim<>(20));
-            CHECK(s3 == s2 && s3 == s1);
+            CHECK(!(s1 != s2));
+            CHECK(!(s1 < s2));
+            CHECK(s1 <= s2);
+            CHECK(!(s1 > s2));
+            CHECK(s1 >= s2);
+            CHECK(s2 == s1);
+            CHECK(!(s2 != s1));
+            CHECK(!(s2 < s1));
+            CHECK(s2 <= s1);
+            CHECK(!(s2 > s1));
+            CHECK(s2 >= s1);
         }
 
         {
-            auto s1 = nullptr;
-            auto s2 = nullptr;
+            int arr[] = {2, 1};
+            span<int> s1 = arr;
+            span<int> s2 = arr;
+
             CHECK(s1 == s2);
             CHECK(!(s1 != s2));
             CHECK(!(s1 < s2));
@@ -914,6 +921,7 @@ SUITE(span_tests)
         }
     }
 
+#if 0
     TEST(fixed_size_conversions)
     {
         int arr[] = {1, 2, 3, 4};