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

Why so much work, so much typing?

bool has_only_spaces(const std::string& str) {
   return str.find_first_not_of (' ') == str.npos;
}