# std::basic_string<CharT,Traits,Allocator>::find_first_not_of

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< 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 | find characters in the string (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)

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