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

Something like:

return std::find_if(
            str.begin(), str.end(),
            std::bind2nd( std::not_equal_to(), ' ' ) )
    == str.end();

If you're interested in white space, and not just the space character, then the best thing to do is to define a predicate, and use it:

struct IsNotSpace
{
    bool operator()( char ch ) const
    {
        return ! ::is_space( static_cast( ch ) );
    }
};

If you're doing any text processing at all, a collection of such simple predicates will be invaluable (and they're easy to generate automatically from the list of functions in ).