Add a few more checks on the subspan range.

src/axom/core/ArrayView.hpp

@@ -135,18 +135,23 @@ class ArrayView : public ArrayBase<T, DIM, ArrayView<T, DIM, SPACE>>
    * \param [in] count The number of elements to include in the subspan, or -1
    *  to take all elements after offset (default).
    *
-   * \return A subspan ArrayView that spans the indices [offset, offset + count),
-   *  or [offset, num_elements) if count == -1.
+   * \return An ArrayView that spans the indices [offset, offset + count),
+   *  or [offset, num_elements) if count < 0.
    *
-   * \pre offset + count <= m_num_elements if count != -1
+   * \pre offset + count <= m_num_elements if count < 0
    */
   template <int UDIM = DIM, typename Enable = typename std::enable_if<UDIM == 1>::type>
   AXOM_HOST_DEVICE ArrayView subspan(IndexType offset, IndexType count = -1) const
   {
-    assert(offset + count <= m_num_elements);
+    assert(offset >= 0 && offset < m_num_elements);
+    if(count >= 0)
+    {
+      assert(offset + count <= m_num_elements);
+    }
+
     ArrayView slice = *this;
     slice.m_data += offset;
-    if(count == -1)
+    if(count < 0)
     {
       slice.m_num_elements -= offset;
     }

src/axom/core/tests/core_array.hpp

@@ -1937,12 +1937,21 @@ TEST(core_array, check_subspan_range)
 {
   int m = 10;
   int n = 3;
+  int l = 5;
   Array<int> arr(m);
+
   ArrayView<int> arrv1(arr);
+  EXPECT_EQ(arrv1.size(), arr.size());
+
   ArrayView<int> arrv2 = arrv1.subspan(n);
   EXPECT_EQ(arrv2.size() + n, arrv1.size());
   EXPECT_EQ(&arrv2[0], &arr[n]);
   EXPECT_EQ(&arrv2[arrv2.size() - 1], &arr[arr.size() - 1]);
+
+  ArrayView<int> arrv3 = arrv1.subspan(n, l);
+  EXPECT_EQ(arrv3.size(), l);
+  EXPECT_EQ(&arrv3[0], &arr[n]);
+  EXPECT_EQ(&arrv3[arrv3.size() - 1], &arr[n + l - 1]);
 }
 
 } /* end namespace axom */