How to test if a string contains any digits in C++

Question

I want to know if a string has any digits, or if there are no digits. Is there a function that easily does this?

Answer 1

There's nothing standard for the purpose, but it's not difficult to make one:

template 
bool has_digits(std::basic_string &input)
{
    typedef typename std::basic_string::iterator IteratorType;
    IteratorType it =
        std::find_if(input.begin(), input.end(),
                     std::tr1::bind(std::isdigit,
                                    std::tr1::placeholders::_1,
                                    std::locale()));
    return it != input.end();
}

And you can use it like so:

std::string str("abcde123xyz");
printf("Has digits: %s\n", has_digits(str) ? "yes" : "no");

Edit:

Or even better version (for it can work with any container and with both const and non-const containers):

template 
bool has_digits(InputIterator first, InputIterator last)
{
    typedef typename InputIterator::value_type CharT;
    InputIterator it =
        std::find_if(first, last,
                     std::tr1::bind(std::isdigit,
                                    std::tr1::placeholders::_1,
                                    std::locale()));
    return it != last;
}

And this one you can use like:

const std::string str("abcde123xyz");
printf("Has digits: %s\n", has_digits(str.begin(), str.end()) ? "yes" : "no");