std::basic_string_view<CharT,Traits>::find_first_of

 

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basic_string

basic_string_view (C++17)

char_traits

 

std::basic_string_view

Member functions basic_string_view::basic_string_view    basic_string_view::operator= Iterators basic_string_view::beginbasic_string_view::cbegin basic_string_view::endbasic_string_view::cend basic_string_view::rbeginbasic_string_view::crbegin basic_string_view::rendbasic_string_view::crend Element access basic_string_view::at basic_string_view::operator[] basic_string_view::front basic_string_view::back basic_string_view::data Capacity basic_string_view::sizebasic_string_view::length basic_string_view::max_size basic_string_view::empty Modifiers basic_string_view::remove_prefix basic_string_view::remove_suffix basic_string_view::swap

Operations basic_string_view::copy basic_string_view::substr basic_string_view::compare basic_string_view::starts_with (C++20) basic_string_view::ends_with (C++20) basic_string_view::contains (C++23) basic_string_view::find basic_string_view::rfind basic_string_view::find_first_of basic_string_view::find_last_of basic_string_view::find_first_not_of basic_string_view::find_last_not_of Constants basic_string_view::npos Non-member functions operator==operator!=operator<operator>operator<=operator>=operator<=> (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20) operator<< operator""sv Helper classes hash<std::string_view>hash<std::wstring_view>hash<std::u8string_view>hash<std::u16string_view>hash<std::u32string_view> (C++20) Deduction guides(C++20)

 

constexpr size_type find_first_of( basic_string_view v, size_type pos = 0 ) const noexcept;	(1)	(since C++17)
constexpr size_type find_first_of( CharT ch, size_type pos = 0 ) const noexcept;	(2)	(since C++17)
constexpr size_type find_first_of( const CharT* s, size_type pos, size_type count ) const;	(3)	(since C++17)
constexpr size_type find_first_of( const CharT* s, size_type pos = 0 ) const;	(4)	(since C++17)

Finds the first character equal to any of the characters in the given character sequence.

1) Finds the first occurrence of any of the characters of v in this view, starting at position pos.

2) Equivalent to find_first_of(basic_string_view(std::addressof(ch), 1), pos).

3) Equivalent to find_first_of(basic_string_view(s, count), pos).

4) Equivalent to find_first_of(basic_string_view(s), pos).

Parameters

v	-	view to search for
pos	-	position at which to start the search
count	-	length of the string of characters to search for
s	-	pointer to a string of characters to search for
ch	-	character to search for

Return value

Position of the first occurrence of any character of the substring, or npos if no such character is found.

Complexity

O(size() * v.size()) at worst.

Example

Run this code

#include <iostream>
#include <string_view>
 
int main()
{
    using namespace std::literals;
    constexpr auto N = std::string_view::npos;
 
    auto is_white_space = [](const char c) noexcept
    {
        return " \t\n\f\r\v"sv.find_first_of(c) != N;
    };
 
    static_assert(
        1 == "alignas"sv.find_first_of("klmn"sv) &&
          //   └─────────────────────────┘
        N == "alignof"sv.find_first_of("wxyz"sv) &&
          //
        3 == "concept"sv.find_first_of("bcde"sv, /* pos= */ 1) &&
          //     └───────────────────────┘
        N == "consteval"sv.find_first_of("oxyz"sv, /* pos= */ 2) &&
          //
        6 == "constexpr"sv.find_first_of('x') &&
          //        └─────────────────────┘
        N == "constinit"sv.find_first_of('x') &&
          //
        6 == "const_cast"sv.find_first_of('c', /* pos= */ 4) &&
          //        └──────────────────────┘
        N == "continue"sv.find_first_of('c', /* pos= */ 42) &&
          //
        5 == "co_await"sv.find_first_of("cba", /* pos= */ 4) &&
          //       └───────────────────────┘
        7 == "decltype"sv.find_first_of("def", /* pos= */ 2, /* count= */ 2) &&
          //         └────────────────────┘
        N == "decltype"sv.find_first_of("def", /* pos= */ 2, /* count= */ 1) &&
          //
        is_white_space(' ') && is_white_space('\r') && !is_white_space('\a')
    );
    std::cout << "All tests passed.\n";
}

Output:

All tests passed.

See also

find (C++17)	find characters in the view (public member function)
rfind (C++17)	find the last occurrence of a substring (public member function)
find_last_of (C++17)	find last occurrence of characters (public member function)
find_first_not_of (C++17)	find first absence of characters (public member function)
find_last_not_of (C++17)	find last absence of characters (public member function)
find_first_of	find first occurrence of characters (public member function of std::basic_string<CharT,Traits,Allocator>)