I'm trying to learn using regex in C++ and I got this code:
std::string s("21\n");
std::regex e("\\b(2)1");
std::cout << std::regex_replace(s, e, "${1}0 first");
I wanna turn
21
into
20 first
but {} seem not to separate capture '$1' like in C#. What should I use then?
And overall can someone point me to C++ regex library documentation? It seems I can't find one. Or maybe somebody can point me to a better library with full documentation?
C++ doesn't permit the ${1} syntax. In general, that can be a problem, so sometimes you have to use a callback instead.
In this particular case, though, you're in luck because the backreference identifier is at most two digits, so with $01 you're safe:
#include <string>
#include <regex>
#include <iostream>
int main()
{
std::string s("21\n");
std::regex e("\\b(2)1");
std::cout << std::regex_replace(s, e, "$010 first") << '\n';
}
// Output: 20 first
As for documentation, cppreference has most of the facts, but in all honesty the available documentation for std::regex is about as esoteric as the feature itself.
std::regex here!