c++ - 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 ^[[:alnum:] ]+$ but without using regular expressions. This is what I have so far:

#include <algorithm>

static inline bool is_not_alnum_space(char c)
{
    return !(isalpha(c) || isdigit(c) || (c == ' '));
}

bool string_is_valid(const std::string &str)
{
    return find_if(str.begin(), str.end(), is_not_alnum_space) == str.end();
}

Is there a better solution, or a “more C++” way to do this?

Answer 1

Looks good to me, but you can use isalnum(c) instead of isalpha and isdigit.