std::basic_string_view::find_first_of(3)

NAME
std::basic_string_view::find_first_of - std::basic_string_view::find_first_of

Synopsis
   constexpr size_type
       find_first_of( basic_string_view v, size_type pos = 0 ) const (1) (since C++17)
   noexcept;
   constexpr size_type (2) (since C++17)
       find_first_of( CharT ch, size_type pos = 0 ) const noexcept;
   constexpr size_type
       find_first_of( const CharT* s, size_type pos, size_type count (3) (since C++17)
   ) const;
   constexpr size_type (4) (since C++17)
       find_first_of( const CharT* s, size_type pos = 0 ) const;
   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 <string_view>
 using namespace std::literals;
 constexpr auto N = std::string_view::npos;
 constexpr bool is_white_space(const char c)
 {
     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')
 );
 int main() {}

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