std::basic_...ind_last_of(3)

🌸 NAME 🌸

okay so bestie, this is std::basic_string_view::find_last_of — and the NAME section is literally std::basic_string_view::find_last_of - std::basic_string_view::find_last_of. Yes, it said the same thing twice, and honestly? iconic. 💅

This page is std::basic_...ind_last_of(3) from the C++ Standard Libary manual (that’s the exact header spelling, no cap 😭), and it’s all about finding the last character in a view that matches any character from a sequence you hand it. 🦋

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✨ Synopsis ✨

Four overloads, all since C++17, all cute. Here are the exact synopsis lines from the page, with the overload markers and qualifiers kept intact:

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

the four overloads are numbered (1) through (4), and every single one is since C++17. The const and noexcept qualifiers are in there exactly as the page has them — don’t let the scrambled line breaks gaslight you. 🫶

It finds the last character equal to one of the characters in the given character sequence.

The page is very clear that the exact search algorithm is not specified — so no guessing at internals, bestie. The search only considers the interval [0, pos]. If the character is not present in that interval, npos will be returned. periodt.

• 1) Finds the last occurrence of any of the characters of v in this view, ending at position pos.
• 2) Equivalent to find_last_of(basic_string_view(std::addressof(ch), 1), pos).
• 3) Equivalent to find_last_of(basic_string_view(s, count), pos).
• 4) Equivalent to find_last_of(basic_string_view(s), pos).

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💖 Parameters 💖

• v — view to search for.
• pos — position at which the search is to finish.
• 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.

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🎀 Return value 🎀

Position of the last occurrence of any character of the substring, or npos if no such character is found. that’s the whole tea. ☕

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🦋 Complexity 🦋

O(size() * v.size()) at worst. yes bestie, that’s the complexity line, exactly. 😭

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🌈 Example 🌈

The page says // Run this code, and the exact code block is this:

        #include <string_view>

        using namespace std::literals;
        constexpr auto N = std::string_view::npos;

        static_assert(
            5 == "delete"sv.find_last_of("cdef"sv) &&
              //       └────────────────────┘
            N == "double"sv.find_last_of("fghi"sv) &&
              //
            0 == "else"sv.find_last_of("bcde"sv, 2 /* pos [0..2]: "els" */) &&
              //  └────────────────────────┘
            N == "explicit"sv.find_last_of("abcd"sv, 4 /* pos [0..4]: "expli"
       */) &&
              //
            3 == "extern"sv.find_last_of('e') &&
              //     └────────────────────┘
            N == "false"sv.find_last_of('x') &&
              //
            0 == "inline"sv.find_last_of('i', 2 /* pos [0..2]: "inl" */) &&
              //  └───────────────────────┘
            N == "mutable"sv.find_last_of('a', 2 /* pos [0..2]: "mut" */) &&
              //
            3 == "namespace"sv.find_last_of("cdef", 3 /* pos [0..3]: "name" */,
       3 /* "cde" */) &&
              //     └─────────────────────────┘
            N == "namespace"sv.find_last_of("cdef", 3 /* pos [0..3]: "name" */,
       2 /* "cd" */)
        );

        int main() {}

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👑 See also 👑

• find — find characters in the view (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_first_not_of — find first absence of characters (public member function).
• find_last_not_of — find last absence of characters (public member function).
• find_last_of — find last occurrence of characters (public member function of std::basic_string<CharT,Traits,Allocator>).

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okay that’s the whole page, bestie. source/version: http://cppreference.com · date: 2024.06.10 · footer page tag: std::basic_...ind_last_of(3). now go slay your string views 💖✨