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 (1) (since C++17)
   pos = 0 ) const noexcept;
   constexpr size_type find_first_of( CharT c, size_type pos = 0 ) (2) (since C++17)
   const noexcept;
   constexpr size_type find_first_of( const CharT* s, size_type pos, (3) (since C++17)
   size_type count ) const;
   constexpr size_type find_first_of( const CharT* s, size_type pos = (4) (since C++17)
   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(c), 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
   c - 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>
 #include <iostream>
 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 find characters in the view
   (C++17) (public member function)
   rfind find the last occurrence of a substring
   (C++17) (public member function)
   find_last_of find last occurrence of characters
   (C++17) (public member function)
   find_first_not_of find first absence of characters
   (C++17) (public member function)
   find_last_not_of find last absence of characters
   (C++17) (public member function)
                     find first occurrence of characters
   find_first_of (public member function of
                     std::basic_string<CharT,Traits,Allocator>)