NAME¶

std::basic_string::find_first_not_of - std::basic_string::find_first_not_of

Synopsis¶

size_type find_first_not_of( const basic_string& str, (1) (noexcept since C++11)
size_type pos = 0 ) const; (constexpr since C++20)
size_type find_first_not_of( const CharT* s,
size_type pos, size_type (2) (constexpr since C++20)
count ) const;
size_type find_first_not_of( const CharT* s, (3) (constexpr since C++20)
size_type pos = 0 ) const;
size_type find_first_not_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_not_of( const StringViewLike& t, (5) (constexpr since C++20)

size_type pos = 0 ) const
noexcept(/* see below */);

Finds the first character equal to none of the characters in the given character
sequence. The search considers only the range [pos, size()). If all characters in
the range can be found in the given character sequence, 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.
If [s, s + count) is not a valid range, the behavior is undefined.
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).
If [s, s + Traits::length(s)) is not a valid range, the behavior is undefined.
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 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 identifying characters to search for
pos - position for the search 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 std::string::npos if no such character is found.

Exceptions¶

1,4) Throws nothing.
5)
noexcept specification:
noexcept(std::is_nothrow_convertible_v<const T&, std::basic_string_view<CharT,
Traits>>)

If an exception is thrown for any reason, this function has no effect (strong
exception safety guarantee).

Example¶

// Run this code

#include <iostream>
#include <string>

int main()
{
// Permit uppercase letters, lowercase letters and numbers in macro names
const char* pattern = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"abcdefghijklmnopqrstuvwxyz"
"0123456789";

std::string data = "1) %FIX, 2) %HACK, and 3) %TODO";
const std::string replacement = "%DONE%";

std::cout << "Before: " << data << '\n';

for (std::string::size_type first{}, last{};
(first = data.find('%', first)) != std::string::npos;
first += replacement.size())
{
last = data.find_first_not_of(pattern, first + 1);
if (last == std::string::npos)
last = data.length();

// Now first at '%' and last is one past end of the found substring
data.replace(first, last - first, replacement);
}

std::cout << "After: " << data << '\n';
}

Output:¶

Before: 1) %FIX, 2) %HACK, and 3) %TODO
After: 1) %DONE%, 2) %DONE%, and 3) %DONE%

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 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_of find first occurrence 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 absence of characters
find_first_not_of (public member function of std::basic_string_view<CharT,Traits>)

Category:¶

* conditionally noexcept