#include <algorithm>
#include <iostream>
#include <regex>
#include <string>
using namespace std;
int main() {
auto foo = "a+\\+"s;
regex bar("((?:[^\\\\\\+]|\\\\.)+)");
copy(sregex_token_iterator(cbegin(foo), cend(foo), bar, 1), sregex_token_iterator(), ostream_iterator<string>(cout, "\n"));
}
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