std::basic_string::find_first_of
std::basic_string::find_first_of
(1) | ||
|
(until C++11) | |
|
(since C++11) | |
|
(2) | |
|
(3) | |
(4) | ||
|
(until C++11) | |
|
(since C++11) | |
|
(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
#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 |
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