implemented front() and back()

src/json.hpp.re2c

@@ -1263,6 +1263,34 @@ class basic_json
         return m_value.object->operator[](key);
     }
 
+    /// access the first element
+    inline reference front()
+    {
+        return *begin();
+    }
+
+    /// access the first element
+    inline const_reference front() const
+    {
+        return *cbegin();
+    }
+
+    /// access the last element
+    inline reference back()
+    {
+        auto tmp = end();
+        --tmp;
+        return *tmp;
+    }
+
+    /// access the last element
+    inline const_reference back() const
+    {
+        auto tmp = cend();
+        --tmp;
+        return *tmp;
+    }
+
     /// remove element given an iterator
     template <class T, typename
               std::enable_if<