std::flat_map::value_comp(3)

💖 std::flat_map::value_comp(3) 💖

okay so this is a C++ Standard Libary manual page, bestie, and we're talking about std::flat_map::value_comp. It's giving C++23 member-function realness, and honestly? iconic. 🫶

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🌸 NAME 🌸

std::flat_map::value_comp — yep, the page NAME is literally std::flat_map::value_comp too. No cap, it's right there. 💅

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✨ Synopsis ✨

          std::flat_map::value_compare value_comp() const;  (since C++23)

That's the whole signature. It's a const member function that returns std::flat_map::value_compare, and it's been around since C++23. 🦋

Here's the tea: it returns a function object that compares objects of type std::flat_map::value_type — those are key-value pairs — by using key_comp to compare the first components of the pairs. 🍓

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🧸 Parameters 🧸

None. Zero. Nada. The parameter list is literally empty, bestie. 😌

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🎁 Return value 🎁

The value comparison function object. That's it. That's the return. 🫶

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🌀 Complexity 🌀

Constant. That's the whole thing. No stress, no drama. 💅

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🎀 Example 🎀

        // Run this code

        #include <iostream>
        #include <flat_map>
        #include <utility>

        // Example module 97 key compare function
        struct ModCmp
        {
            bool operator()(int lhs, int rhs) const
            {
                return (lhs % 97) < (rhs % 97);
            }
        };

        int main()
        {
            std::flat_map<int, char, ModCmp> cont;
            cont = {{1, 'a'}, {2, 'b'}, {3, 'c'}, {4, 'd'}, {5, 'e'}};

            auto comp_func = cont.value_comp();

            for (const std::pair<int, char> val = {100, 'a'}; auto it : cont)
            {
                const bool before = comp_func(it, val);
                const bool after = comp_func(val, it);

                std::cout << '(' << it.first << ',' << it.second << ") ";
                if (!before && !after)
                    std::cout << "equivalent to key (" << val.first << ")\n";
                else if (before)
                    std::cout << "goes before key (" << val.first << ")\n";
                else if (after)
                    std::cout << "goes after key (" << val.first << ")\n";
                else
                    std::unreachable();
            }
        }

💻 Output 💻

        (1,a) goes before key (100)
        (2,b) goes before key (100)
        (3,c) equivalent to key (100)
        (4,d) goes after key (100)
        (5,e) goes after key (100)

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👀 See also 👀

• key_comp — returns the function that compares keys (public member function). 🌟

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mwah 💋 this page came from source http://cppreference.com, version/date 2024.06.10 — now go be the main character of your own flat_map, bestie 🌈👑