use native optional

Author: aminya

src/core/optional.h

@@ -1,29 +1,7 @@
 #ifndef SUPERSTRING_OPTIONAL_H
 #define SUPERSTRING_OPTIONAL_H
 
-#include <utility>
+#include <optional>
+using std::optional;
 
-template <typename T> class optional {
-  T value;
-  bool is_some;
-
-public:
-  optional(T &&value) : value(std::move(value)), is_some(true) {}
-  optional(const T &value) : value(value), is_some(true) {}
-  optional() : value(T()), is_some(false) {}
-
-  T &operator*() { return value; }
-  const T &operator*() const { return value; }
-  const T *operator->() const { return &value; }
-  T *operator->() { return &value; }
-  operator bool() const { return is_some; }
-  bool operator==(const optional<T> &other) {
-    if (is_some) {
-      return other.is_some && value == other.value;
-    } else {
-      return !other.is_some;
-    }
-  }
-};
-
-#endif // SUPERSTRING_OPTIONAL_H
+#endif  // SUPERSTRING_OPTIONAL_H