std::basic_...nd_first_of(3) C++ Standard Libary std::basic_...nd_first_of(3) NAME std::basic_string::find_first_of - std::basic_string::find_first_of Synopsis size_type find_first_of( const basic_string& str, (1) (noexcept since C++11) size_type pos = 0 ) const; (constexpr since C++20) size_type find_first_of( const CharT* s, size_type pos, size_type count (2) (constexpr since C++20) ) const; size_type find_first_of( const CharT* s, size_type pos = (3) (constexpr since C++20) 0 ) const; size_type find_first_of( CharT ch, size_type pos = 0 ) (4) (noexcept since C++11) const; (constexpr since C++20) template< class StringViewLike > size_type (since C++17) find_first_of( const StringViewLike& t, (5) (constexpr since C++20) size_type pos = 0 ) const noexcept(/* see below */); Finds the first character equal to one of the characters in the given character sequence. The search considers only the range [pos, size()). If none of the characters in the given character sequence is present in the range, npos will be returned. 1) Finds the first character equal to one of the characters in str. 2) Finds the first character equal to one of the characters in 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 first character equal to one of the characters in 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 un- defined. 4) Finds the first 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 first character equal to one of the characters in 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. Parameters str - string identifying characters to search for pos - position at which to begin searching count - length of character string identifying characters to search for s - pointer to a character string identifying characters to search for ch - character to search for t - object (convertible to std::basic_string_view) identifying char- acters to search for Return value Position of the found character or npos if no such character is found. 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 effect (strong exception safety guarantee). Notes Traits::eq() is used to perform the comparison. Example // Run this code #include <cassert> #include <iostream> #include <string> #include <string_view> int main() { using namespace std::literals; std::string::size_type sz; // (1) sz = "alignas"s.find_first_of("klmn"s); // aaaaaaaaaaaaaaaaaaaaaaaaaa assert(sz == 1); sz = "alignof"s.find_first_of("wxyz"s); // no match assert(sz == std::string::npos); // (2) sz = "consteval"s.find_first_of("xyzabc", 0, 3); // no match (A are not targets) AAA assert(sz == std::string::npos); sz = "consteval"s.find_first_of("xyzabc", 0, 6); // aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa assert(sz == 0); // (3) sz = "decltype"s.find_first_of("xyzabc"); // aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa assert(sz == 2); // (4) sz = "co_await"s.find_first_of('a'); // aaaaaaaaaaaaaaaaaaaaaaaa assert(sz == 3); // (5) sz = "constinit"s.find_first_of("int"sv); // aaaaaaaaaaaaaaaaaaaaaaaaaaa assert(sz == 2); std::cout << "All tests passed.\n"; } Output: All tests passed. 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 removed LWG 2946 C++17 overload (5) caused ambiguity in some avoided by making it a cases template P1148R0 C++11 noexcept for overloads (4,5) were restored C++17 accidentally dropped by LWG2064/LWG2946 See also find finds the first occurrence of the given substring (public member function) rfind find the last occurrence of a substring (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 first occurrence of characters find_first_of (public member function of std::ba- sic_string_view<CharT,Traits>) returns the length of the maximum initial segment that consists strspn of only the characters found in another byte string (function) Category: * conditionally noexcept http://cppreference.com 2024.06.10 std::basic_...nd_first_of(3)
NAME | Synopsis | Parameters | Return value | Exceptions | Notes | Example | Output: | See also | Category:
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