From 7004ef506ce2a0deb60d52964c521ea69e9a39ed 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 1/3] adding front and back

---
 include/gsl/span     | 13 +++++++++++++
 tests/span_tests.cpp | 15 ++++++++++++++-
 2 files changed, 27 insertions(+), 1 deletion(-)

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 d22dc08..f7d0026 100644
--- a/tests/span_tests.cpp
+++ b/tests/span_tests.cpp
@@ -893,7 +893,7 @@ TEST_CASE("subspan")
     {
         span<int, 5> av = arr;
         CHECK((av.subspan<1>().size() == 4));
-        CHECK(decltype(av.subspan<1>())::extent == 4);    
+        CHECK(decltype(av.subspan<1>())::extent == 4);
     }
 
     {
@@ -1562,3 +1562,16 @@ TEST_CASE("default_constructible")
     CHECK((!std::is_default_constructible<span<int, 42>>::value));
 }
 
+
+TEST_CASE("front_back")
+{
+    int arr[5] = {1,2,3,4,5};
+    span<int> s{arr};
+    CHECK(s.front() == 1);
+    CHECK(s.back() == 5);
+
+    span<int> s2;
+    CHECK_THROWS_AS(s2.front(), fail_fast);
+    CHECK_THROWS_AS(s2.back(), fail_fast);
+}
+

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 2/3] 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__

From c7f9b3301ac10f464fff0a7d2d3f5e0eb4e24b97 Mon Sep 17 00:00:00 2001
From: "Jordan Maples [MSFT]" <49793787+JordanMaples@users.noreply.github.com>
Date: Thu, 9 Jan 2020 12:13:12 -0800
Subject: [PATCH 3/3] noexcepting new functions

---
 include/gsl/span | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/gsl/span b/include/gsl/span
index c16ded4..8536cf7 100644
--- a/include/gsl/span
+++ b/include/gsl/span
@@ -513,13 +513,13 @@ 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
+    constexpr reference front() const noexcept
     {
         Expects(size() > 0);
         return data()[0];
     }
 
-    constexpr reference back() const
+    constexpr reference back() const noexcept
     {
         Expects(size() > 0);
         return data()[size() - 1];