How to test if a string contains any digits in C++
I want to know if a string has any digits, or if there are no digits. Is there a funct开发者_开发百科ion that easily does this?
Perhaps the following:
if (std::string::npos != s.find_first_of("0123456789")) {
std::cout << "digit(s)found!" << std::endl;
}
boost::regex re("[0-9]");
const std::string src = "test 123 test";
boost::match_results<std::string::const_iterator> what;
bool search_result =
boost::regex_search(src.begin(), src.end(), what, re, boost::match_default);
#include <cctype>
#include <algorithm>
#include <string>
if (std::find_if(s.begin(), s.end(), (int(*)(int))std::isdigit) != s.end())
{
// contains digit
}
find_first_of
is probably your best bet, but I've been playing around with iostream facets so here's an alternative:
if ( use_facet< ctype<char> >( locale() ).scan_is( ctype<char>::digit,
str.data(), str.data() + str.size() ) != str.data + str.size() )
Change string
to wstring
and char
to wchar
and you might theoretically have a chance at handling those weird fixed-width digits used in some Asian scripts.
given std::String s;
if( s.find_first_of("0123456789")!=std::string::npos )
//digits
There's nothing standard for the purpose, but it's not difficult to make one:
template <typename CharT>
bool has_digits(std::basic_string<CharT> &input)
{
typedef typename std::basic_string<CharT>::iterator IteratorType;
IteratorType it =
std::find_if(input.begin(), input.end(),
std::tr1::bind(std::isdigit<CharT>,
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 <typename InputIterator>
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<CharT>,
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");
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