include/HZZException.h

#ifndef HZZ2L2NU_INCLUDE_HZZEXCEPTION_H_
#define HZZ2L2NU_INCLUDE_HZZEXCEPTION_H_

#include <sstream>
#include <string>
#include <stdexcept>


class HZZException : public std::exception {
 public:
  HZZException(std::string message = "")
     : message_{message} {}

  template<typename T>
  HZZException &operator<<(T const &token) {
    message_ << token;
    return *this;
  }

  char const *what() const noexcept override {
    buffer_ = message_.str();  // Needed to preserve the temporary object
    return buffer_.c_str();
  }

 private:
  std::ostringstream message_;

  mutable std::string buffer_;
};

#endif  // HZZ2L2NU_INCLUDE_HZZEXCEPTION_H_

---