std::basic_string<CharT,Traits,Allocator>::find_first_not_of
From cppreference.com
< cpp | string | basic string
(1) | ||
size_type find_first_not_of( const basic_string& str, size_type pos = 0 ) const; |
(until C++11) | |
size_type find_first_not_of( const basic_string& str, size_type pos = 0 ) const noexcept; |
(since C++11) | |
size_type find_first_not_of( const CharT* s, size_type pos, size_type count ) const; |
(2) | |
size_type find_first_not_of( const CharT* s, size_type pos = 0 ) const; |
(3) | |
(4) | ||
size_type find_first_not_of( CharT ch, size_type pos = 0 ) const; |
(until C++11) | |
size_type find_first_not_of( CharT ch, size_type pos = 0 ) const noexcept; |
(since C++11) | |
template < class T > size_type find_first_not_of( const T& t, size_type pos = 0 ) const noexcept(/* see below */); |
(5) | (since C++17) |
Finds the first character equal to none 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 none of characters in
str
. 2) Finds the first character equal to none of characters in range
[s, s+count)
. This range can include null characters.3) Finds the first character equal to none of 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 not 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 none of 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.In all cases, equality is checked by calling Traits::eq.
Parameters
str | - | string identifying characters to search for |
pos | - | position for the seach to start from |
count | - | length of character string identifying characters to search for |
s | - | pointer to a character string identifying characters to search for |
ch | - | character identifying characters 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>>)
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 <string> #include <iostream> int main() { std::string to_search = "Some data with %MACROS to substitute"; std::cout << "Before: " << to_search << '\n'; auto pos = std::string::npos; while ((pos = to_search.find('%')) != std::string::npos) { // Permit uppercase letters, lowercase letters and numbers in macro names const auto after = to_search.find_first_not_of("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789", pos + 1); // Now to_search[pos] == '%' and to_search[after] == ' ' (after the 'S') if(after != std::string::npos) to_search.replace(pos, after - pos, "some very nice macros"); } std::cout << "After: " << to_search << '\n'; }
Output:
Before: Some data with %MACROS to substitute After: Some data with some very nice macros to substitute
See also
find characters in the string (public member function) | |
find the last occurrence of a substring (public member function) | |
find first occurrence of characters (public member function) | |
find last occurrence of characters (public member function) | |
find last absence of characters (public member function) |