Function string_not_empty

example/mutual.cc:59–62

* @brief not empty validator. * @param value * @return */

 * @return
 */
bool string_not_empty(const char*, const std::string& value) {
  if (0 == value.length()) { return false; }
  return true;
}

DEFINE_validator(input_edges,  &string_not_empty);
DEFINE_validator(output,  &string_not_empty);