std::basic_...last_not_of(3)

💅 std::basic_string_view::find_last_not_of — the manual, but make it make sense

okay bestie, welcome to the std::basic_string_view::find_last_not_of page 💖 this is the C++ Standard Library manual, and today we're reading the std::basic_string_view::find_last_not_of entry together. yes the title is the same thing twice, that's just how these pages are, don't @ me 🫶

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✨ SYNOPSIS ✨

four overloads, all since C++17 🌸 watch the const and noexcept placement, she's specific:

(1) constexpr size_type
        find_last_not_of( basic_string_view v, size_type pos = npos ) const noexcept;

(2) constexpr size_type
        find_last_not_of( CharT ch, size_type pos = npos ) const noexcept;

(3) constexpr size_type
        find_last_not_of( const CharT* s, size_type pos, size_type count ) const;

(4) constexpr size_type
        find_last_not_of( const CharT* s, size_type pos = npos ) const;

the whole vibe: finds the last character not equal to any of the characters in the given character sequence. and lowkey the search only ever considers the interval [0, pos] — nothing outside it, periodt 💅

• (1) finds the last character in this view that's not equal to any of the characters of v, starting at position pos.
• (2) equivalent to find_last_not_of(basic_string_view(std::addressof(ch), 1), pos).
• (3) equivalent to find_last_not_of(basic_string_view(s, count), pos).
• (4) equivalent to find_last_not_of(basic_string_view(s), pos).

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🎀 PARAMETERS 🎀

• v — the view to search for 🔍
• pos — position at which to start the search 📍
• count — length of the string of characters to compare 📏
• s — pointer to a string of characters to compare
• ch — character to compare

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🌟 RETURN VALUE 🌟

the position of the last character not equal to any of the characters in the given string — iconic, she found it ✨ or npos if no such character is found 😭 (that's the "nope, nothing, sorry bestie" answer).

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🦋 COMPLEXITY 🦋

O(size() * v.size()) at worst. yes, that's the worst case, ngl it can get expensive, plan accordingly 💀

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🌈 EXAMPLE 🌈

// Run this code

#include <string_view>
using std::operator""sv;

int main()
{
    static_assert(1 == "BCDEF"sv.find_last_not_of("DEF"));
                    //   ^
    static_assert(2 == "BCDEFG"sv.find_last_not_of("EFG", 3));
                    //    ^
    static_assert(2 == "ABBA"sv.find_last_not_of('A'));
                    //    ^
    static_assert(1 == "ABBA"sv.find_last_not_of('A', 1));
                    //   ^
}

the little ^ comments are doing the most and honestly? they ate 🍓 they're pointing at exactly which character lands where. static_assert means this whole thing is checked at compile time, so if you break it, the compiler will let you know loudly 🙈

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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_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 of std::basic_string<CharT,Traits,Allocator>)

⚠️ heads up: that last one is a different find_last_not_of — it belongs to std::basic_string<CharT,Traits,Allocator>, not the string_view. same name, different family member, don't mix them up bestie 🫶

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okay that's the whole page!! 💜 source is cppreference.com, dated 2024.06.10, and this was the std::basic_...last_not_of(3) page from the C++ Standard Library manual. go write some static_asserts, you're gonna slay 🌸✨🎀