--- a/cpp/to_int/to_int.hpp	Wed Aug 01 14:06:11 2018 +0200
+++ b/cpp/to_int/to_int.hpp	Wed Aug 01 14:06:59 2018 +0200
@@ -39,9 +39,9 @@
  * \return the value or std::none if not convertible
  */
 template <typename T = int>
-std::optional<T> to_int(const std::string& str,
-                          T min = std::numeric_limits<T>::min(),
-                          T max = std::numeric_limits<T>::max()) noexcept
+auto to_int(const std::string& str,
+            T min = std::numeric_limits<T>::min(),
+            T max = std::numeric_limits<T>::max()) noexcept -> std::optional<T>
 {
     static_assert(std::is_signed<T>::value, "must be signed");
 
@@ -64,9 +64,9 @@
  * \return the value or std::none if not convertible
  */
 template <typename T = unsigned>
-std::optional<T> to_uint(const std::string& str,
-                           T min = std::numeric_limits<T>::min(),
-                           T max = std::numeric_limits<T>::max()) noexcept
+auto to_uint(const std::string& str,
+             T min = std::numeric_limits<T>::min(),
+             T max = std::numeric_limits<T>::max()) noexcept -> std::optional<T>
 {
     static_assert(std::is_unsigned<T>::value, "must be unsigned");