std::swap(s...c_ifstream)(3)

okay so bestie, welcome to std::swap(s...c_ifstream)(3) from the C++ Standard Libary (yes, that's literally how the manual spells it up top, and we respect the typo 💅). It's giving very specific-helper-overload energy, and we're gonna get through every detail together. 🫶

🌸 NAME 🌸

std::swap(std::basic_ifstream) — std::swap(std::basic_ifstream) (the NAME line really said it twice, so we're keeping it twice, periodt ✨).

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✨ Synopsis ✨

          template< class CharT, class Traits >
          void swap( basic_ifstream<CharT, Traits>& lhs, basic_ifstream<CharT,
       Traits>& rhs
          );

So this is the overload that specializes the std::swap algorithm for std::basic_ifstream. No cap, that's the whole point. It exchanges the state of lhs with that of rhs, and effectively calls lhs.swap(rhs). 🦋

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🫶 Parameters 🫶

• lhs, rhs — the streams whose state to swap. That's it, those are the two besties getting their states traded. 💖

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💖 Return value 💖

(none) — literally nothing comes back. No return value, no drama, just vibes. 🎀

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😭 Exceptions 😭

May throw implementation-defined exceptions. So like, the implementation gets to decide the exception details — that's the caveat, fr fr. 💀

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🧚 Example 🧚

This example is iconic, and yes, the // Run this code line is part of the package:

        // Run this code

        #include <fstream>
        #include <iostream>
        #include <string>

        bool create_stream(std::ifstream& fs)
        {
            try
            {
                std::string some_name = "/tmp/test_file.txt";
                std::ios_base::openmode some_flags = fs.trunc; // | other flags

                if (std::ifstream ts{some_name, some_flags}; ts.is_open())
                {
                    std::swap(ts, fs); // stream objects are not copyable =>
       swap
                    return true;
                }
            }
            catch (...)
            {
                std::cout << "Exception!\n";
            }
            return false;
        }

        int main()
        {
            if (std::ifstream fs; create_stream(fs))
            {
                // use fs stream
            }
        }

The comment says stream objects are not copyable, so swap is the move — and that's the whole demo. 🧚✨

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👑 See also 👑

• swap — swaps two file streams (C++11) (public member function) 🌈

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💌 okay that's the page, bestie. It came from http://cppreference.com, dated 2024.06.10, and it's the std::swap(s...c_ifstream)(3) manual page. Byeee, slay responsibly. 🫶💅