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    cpp/string/basic string view/rfind: Difference between revisions

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    Jujudo (talk | contribs)
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    mNo edit summary
    not sure what was ambiguous about "from right to left" that doesn't also apply to "from end to beginning", but maybe "from pos to beginning" is less ambiguous?
     
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    Finds the last substring equal to the given character sequence. Search begins at {{tt|pos}}, i.e. the found substring must not begin in a position following {{tt|pos}}. If {{lc|npos}} or any value not smaller than {{lc|size()}}-1 is passed as {{tt|pos}}, whole string will be searched.
    Finds the last substring equal to the given character sequence. begins at {{|pos}} , the found substringbegin in a position following {{|pos}}. If {{lc|npos}} or any value not smaller than {{lc|size()}}- 1is passed as {{|pos}}, whole string will be searched.


    @1@Finds the last occurrence of {{tt|v}} in this view, starting at position {{tt|pos}}.
    @1@ Finds the last occurrence of {{|v}} in this view, starting at position {{|pos}}.
    @2@Equivalent to {{c|rfind(basic_string_view(std::addressof(c), 1), pos)}}.
    @2@ Equivalent to {{c|rfind(basic_string_view(std::addressof(), 1), pos)}}.
    @3@Equivalent to {{c|rfind(basic_string_view(s, count), pos)}}.
    @3@ Equivalent to {{c|rfind(basic_string_view(s, count), pos)}}.
    @4@Equivalent to {{c|rfind(basic_string_view(s), pos)}}.
    @4@ Equivalent to {{c|rfind(basic_string_view(s), pos)}}.


    ===Parameters===
    ===Parameters===
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             && (6 == "AB AB AB"sv.rfind("ABCD", N, 2))
             && (6 == "AB AB AB"sv.rfind("ABCD", N, 2))
             && (3 == "AB AB AB"sv.rfind("AB", 5))
             && (3 == "AB AB AB"sv.rfind("AB", 5))
             && (2 == "B AB AB "sv.rfind("AB", 2))
             && (2 == "B AB AB "sv.rfind("AB", 2))
             && (N == "B AB AB "sv.rfind("AB", 1))
             && (N == "B AB AB "sv.rfind("AB", 1))

    Latest revision as of 17:04, 26 April 2026

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

    Finds the last substring that is equal to the given character sequence. The search begins at pos and proceeds towards the beginning (thus, the found substring, if any, cannot begin in a position following pos). If npos or any value not smaller than size()- 1 is passed as pos, the whole string will be searched.

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

    Parameters

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

    Return value

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

    Complexity

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

    Example

    Run this code
    #include <string_view>

int main()
{
    using namespace std::literals;
    constexpr auto N = std::string_view::npos;

    static_assert(true
        && (6 == "AB AB AB"sv.rfind("AB"))
        && (6 == "AB AB AB"sv.rfind("ABCD", N, 2))
        && (3 == "AB AB AB"sv.rfind("AB", 5))
        && (0 == "AB CD EF"sv.rfind("AB", 0))
        && (2 == "B AB AB "sv.rfind("AB", 2))
        && (N == "B AB AB "sv.rfind("AB", 1))
        && (5 == "B AB AB "sv.rfind('A'))
        && (4 == "AB AB AB"sv.rfind('B', 4))
        && (N == "AB AB AB"sv.rfind('C'))
    );
}

    See also

    		 find characters in the view
    (public member function) [edit]
    		find first occurrence of characters
    (public member function) [edit]
    		find last occurrence of characters
    (public member function) [edit]
    		find first absence of characters
    (public member function) [edit]
    		find last absence of characters
    (public member function) [edit]
    		find the last occurrence of a substring
    (public member function of std::basic_string<CharT,Traits,Allocator>) [edit]