//
// 6.1.regex.cpp
// chapter 06 regular expression
// modern c++ tutorial
//
// created by changkun at changkun.de
// https://github.com/changkun/modern-cpp-tutorial
//

#include <iostream>
#include <string>
#include <regex>

int main() {
 std::string fnames[] = {"foo.txt", "bar.txt", "test", "a0.txt", "AAA.txt"};
 // In C++, `\` will be used as an escape character in the string. 
 // In order for `\.` to be passed as a regular expression, 
 // it is necessary to perform second escaping of `\`, thus we have `\\.`
 std::regex txt_regex("[a-z]+\\.txt");
 for (const auto &fname: fnames)
 std::cout << fname << ": " << std::regex_match(fname, txt_regex) << std::endl;
 
 std::regex base_regex("([a-z]+)\\.txt");
 std::smatch base_match;
 for(const auto &fname: fnames) {
 if (std::regex_match(fname, base_match, base_regex)) {
 // the first element of std::smatch matches the entire string
 // the second element of std::smatch matches the first expression with brackets
 if (base_match.size() == 2) {
 std::string base = base_match[1].str();
 std::cout << "sub-match[0]: " << base_match[0].str() << std::endl;
 std::cout << fname << " sub-match[1]: " << base << std::endl;
 }
 }
 }
 
 return 0;
}