Efficient way to check if std::string has only spaces

Question

I was just talking with a friend about what would be the most efficient way to check if a std::string has only spaces. He needs to do this on an embedded project he is worki

Answer 1

To check if string has only whitespace in c++11:

bool is_whitespace(const std::string& s) {
  return std::all_of(s.begin(), s.end(), isspace);
}

in pre-c++11:

bool is_whitespace(const std::string& s) {
  for (std::string::const_iterator it = s.begin(); it != s.end(); ++it) {
    if (!isspace(*it)) {
      return false;
    }
  }
  return true;
}