std::match_results::prefix - cppreference.com

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# std::match_results::prefix

From cppreference.com
< cpp‎ | regex‎ | match results

const_reference prefix() const; |  | (since C++11)

### [edit] Parameters

(none)

### [edit] Return value

Returns a sub_match representing the part of the target sequence between the beginning of the target sequence and the entire match of the regular expression.

### [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

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