From 4b823b165177626de2e14b81c2acf0c92a87644f Mon Sep 17 00:00:00 2001
From: "Jordan Maples [MSFT]" <49793787+JordanMaples@users.noreply.github.com>
Date: Tue, 19 Nov 2019 16:03:55 -0800
Subject: [PATCH] adding front and back

---
 include/gsl/span     | 13 +++++++++++++
 tests/span_tests.cpp | 16 ++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/include/gsl/span b/include/gsl/span
index 59bd121..c16ded4 100644
--- a/include/gsl/span
+++ b/include/gsl/span
@@ -512,6 +512,19 @@ public:
 
     constexpr reference at(index_type idx) const { return this->operator[](idx); }
     constexpr reference operator()(index_type idx) const { return this->operator[](idx); }
+
+    constexpr reference front() const
+    {
+        Expects(size() > 0);
+        return data()[0];
+    }
+
+    constexpr reference back() const
+    {
+        Expects(size() > 0);
+        return data()[size() - 1];
+    }
+
     constexpr pointer data() const noexcept { return storage_.data(); }
 
     // [span.iter], span iterator support
diff --git a/tests/span_tests.cpp b/tests/span_tests.cpp
index edbd118..ebeb685 100644
--- a/tests/span_tests.cpp
+++ b/tests/span_tests.cpp
@@ -1644,6 +1644,22 @@ TEST(span_test, from_array_constructor)
      EXPECT_FALSE((std::is_default_constructible<span<int, 42>>::value));
  }
 
+ TEST(span_test, front_back)
+ {
+    int arr[5] = {1,2,3,4,5};
+    span<int> s{arr};
+    EXPECT_TRUE(s.front() == 1);
+    EXPECT_TRUE(s.back() == 5);
+
+    std::set_terminate([] {
+        std::cerr << "Expected Death. front_back";
+        std::abort();
+    });
+    span<int> s2;
+    EXPECT_DEATH(s2.front(), deathstring);
+    EXPECT_DEATH(s2.back(), deathstring);
+ }
+
 #if __clang__ || __GNUC__
 #pragma GCC diagnostic pop
 #endif // __clang__ || __GNUC__