#include <iostream>
#include <string>
#include <regex>
 
int main()
{
    std::regex const pattern { "[abc]" };
    std::cout << "'[abc]' match with '': " << std::boolalpha << 
        std::regex_match("", pattern) << std::endl;
        
    std::cout << "'[abc]' match with 'a': " << std::boolalpha << 
        std::regex_match("a", pattern) << std::endl;
        
    std::cout << "'[abc]' match with 'b': " << std::boolalpha << 
        std::regex_match("b", pattern) << std::endl;
        
    std::cout << "'[abc]' match with 'z': " << std::boolalpha << 
        std::regex_match("z", pattern) << std::endl;
        
    std::cout << "'[abc]' match with 'ab': " << std::boolalpha << 
        std::regex_match("ab", pattern) << std::endl;
}