std::match_results<BidirIt,Alloc>::prefix
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std::match_results
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match_results::prefix
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(until C++20)
const_reference prefix() const;
(since C++11)
Obtains a reference to the std::sub_match object representing the target sequence between the start of the beginning of the target sequence and the start of the entire match of the regular expression.
ready() must be true. Otherwise, the behavior is undefined.
[edit] Return value
Reference to the unmatched prefix.
[edit] Example
Run this code
#include <iostream> #include <regex> #include <string> int main() { std::regex re("a(a)*b"); std::string target("baaaby"); std::smatch sm; std::regex_search (target, sm, re); std::cout << sm.prefix().str() << '\n'; }
Output:
b