Determine if a string contains only alphanumeric characters (or a space)

Question

I am writing a function that determines whether a string contains only alphanumeric characters and spaces. I am effectively testing whether it matches the regular expression

Answer 1

You can also do this with binders so you can drop the helper function. I'd recommend Boost Binders as they are much easier to use then the standard library binders:

bool string_is_valid(const std::string &str)
{
    return find_if(str.begin(), str.end(),
        !boost::bind(isalnum, _1) || boost::bind(std::not_equal_to, _1, ' ')) == str.end();
}