std::basic_string<CharT,Traits,Allocator>::find_first_of
< cpp | string | basic string
(1) | ||
size_type find_first_of( const basic_string& str, size_type pos = 0 ) const; |
(until C++11) | |
size_type find_first_of( const basic_string& str, size_type pos = 0 ) const noexcept; |
(since C++11) | |
size_type find_first_of( const CharT* s, size_type pos, size_type count ) const; |
(2) | |
size_type find_first_of( const CharT* s, size_type pos = 0 ) const; |
(3) | |
(4) | ||
size_type find_first_of( CharT ch, size_type pos = 0 ) const; |
(until C++11) | |
size_type find_first_of( CharT ch, size_type pos = 0 ) const noexcept; |
(since C++11) | |
template < class T > size_type find_first_of( const T& t, size_type pos = 0 ) const noexcept(/* see below */); |
(5) | (since C++17) |
Finds the first character equal to one of the characters in the given character sequence. The search considers only the interval [pos
, size()). If the character is not present in the interval, 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.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)
.4) Finds the first character equal to
ch
.5) Implicitly converts
t
to a string view sv
as if by std::basic_string_view<CharT, Traits> sv = t;, then finds the first character equal to one of the characters in sv
. This overload only participates in overload resolution if std::is_convertible_v<const T&, std::basic_string_view<CharT, Traits>> is true and std::is_convertible_v<const T&, 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 characters to search for |
Return value
Position of the found character or npos if no such character is found.
Exceptions
5)
noexcept specification:
noexcept(std::is_nothrow_convertible_v<const T&, std::basic_string_view<CharT, Traits>>)
Notes
Traits::eq() is used to perform the comparison.
Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR | Applied to | Behavior as published | Correct behavior |
---|---|---|---|
LWG 2946 | C++17 | string_view overload causes ambiguity in some cases
|
avoided by making it a template |
Example
Run this code
#include <iostream> #include <string> int main() { // the test string std::string str = std::string("Hello World!"); // strings and chars to search for std::string search_str = std::string("o"); const char* search_cstr = "Good Bye!"; std::cout << str.find_first_of(search_str) << '\n'; std::cout << str.find_first_of(search_str, 5) << '\n'; std::cout << str.find_first_of(search_cstr) << '\n'; std::cout << str.find_first_of(search_cstr, 0, 4) << '\n'; // 'x' is not in "Hello World', thus it will return std::string::npos std::cout << str.find_first_of('x') << '\n'; }
Possible output:
4 7 1 4 18446744073709551615
See also
find characters in the string (public member function) | |
find the last occurrence of a substring (public member function) | |
find first absence of characters (public member function) | |
find last occurrence of characters (public member function) | |
find last absence of characters (public member function) | |
returns the length of the maximum initial segment that consists of only the characters found in another byte string (function) |