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std::basic_string::rfind(3) C++ Standard Libary std::basic_string::rfind(3) NAME std::basic_string::rfind - std::basic_string::rfind Synopsis size_type rfind( const basic_string& str, size_type pos (1) (noex- cept since C++11) = npos ) const; (const- expr since C++20) size_type rfind( const CharT* s, size_type pos, (2) (const- expr since C++20) size_type count ) const; size_type rfind( const CharT* s, size_type pos = npos ) (3) (const- expr since C++20) const; size_type rfind( CharT ch, size_type pos = npos ) const; (4) (noex- cept since C++11) (const- expr since C++20) template< class StringViewLike > size_type rfind( const StringViewLike& t, (5) (since C++17) (const- expr since C++20) size_type pos = npos ) const noexcept(/* see below */); Finds the last substring that is equal to the given character se- quence. The search begins at pos and proceeds from right to left (thus, the found sub- string, if any, cannot begin in a position following pos). If npos or any value not smaller than size() - 1 is passed as pos, the whole string will be searched. 1) Finds the last substring equal to str. 2) Finds the last substring equal to the range [s, s + count). This range can include null characters. If [s, s + count) is not a valid range, the behavior is undefined. 3) Finds the last substring equal to the character string pointed to by s. The length of the string is determined by the first null character using Traits::length(s). If [s, s + Traits::length(s)) is not a valid range, the behavior is undefined. 4) Finds the last character equal to ch. 5) Implicitly converts t to a string view sv as if by std::ba- sic_string_view<CharT, Traits> sv = t;, then finds the last substring equal to the contents of sv. This overload participates in overload resolution only if std::is_convertible_v<const StringViewLike&, std::basic_string_view<CharT, Traits>> is true and std::is_convertible_v<const StringViewLike&, const CharT*> is false. In all cases, equality is checked by calling Traits::eq. Parameters str - string to search for pos - position at which to begin searching count - length of substring to search for s - pointer to a character string to search for ch - character to search for t - object (convertible to std::basic_string_view) to search for Return value Position of the first character of the found substring or npos if no such substring is found. Note that this is an offset from the start of the string, not the end. If searching for an empty string (i.e., str.size(), count, or Traits::length(s) is zero), the empty string is found immediately and rfind returns: * pos, if pos < size(); * size() otherwise, including the case where pos == npos. Otherwise, if size() is zero, npos is always returned. Exceptions 1,4) Throws nothing. 5) noexcept specification: noexcept(std::is_nothrow_convertible_v<const T&, std::ba- sic_string_view<CharT, Traits>>) If an exception is thrown for any reason, this function has no ef- fect (strong exception safety guarantee). Example // Run this code #include <iomanip> #include <iostream> #include <string> void print(std::string::size_type n, std::string::size_type len, std::string const &s) { if (n == std::string::npos) std::cout << "not found\n"; else std::cout << "found: " << std::quoted(s.substr(n, len)) << " at " << n << '\n'; } int main() { std::string::size_type n; std::string const s = "This is a string"; // search backwards from end of string n = s.rfind("is"); print(n, 2, s); // search backwards from position 4 n = s.rfind("is", 4); print(n, 2, s); // find a single character n = s.rfind('s'); print(n, 1, s); // find a single character n = s.rfind('q'); print(n, 1, s); // find the prefix (see also s.starts_with("This")) n = s.rfind("This", 0); print(n, 4, s); } Output: found: "is" at 5 found: "is" at 2 found: "s" at 10 not found found: "This" at 0 Defect reports The following behavior-changing defect reports were applied retroac- tively to previously published C++ standards. DR Applied to Behavior as published Correct behavior LWG 847 C++98 there was no exception safety guarantee added strong exception safety guarantee LWG 2064 C++11 overloads (3,4) were noexcept re- moved LWG 2946 C++17 overload (5) caused ambiguity in some avoided by making it a cases tem- plate P1148R0 C++11 noexcept for overloads (4,5) were re- stored C++17 accidently dropped by LWG2064/LWG2946 See also find finds the first occurrence of the given substring (public member function) find_first_of find first occurrence of characters (public member function) find_first_not_of find first absence of characters (public member function) find_last_of find last occurrence of characters (public member function) find_last_not_of find last absence of characters (public member function) find the last occurrence of a substring rfind (public member function of std::ba- sic_string_view<CharT,Traits>) Category: * conditionally noexcept http://cppreference.com 2024.06.10 std::basic_string::rfind(3)
NAME | Synopsis | Parameters | Return value | Exceptions | Example | Output: | See also | Category:
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