std::chrono...::operator--(3)

🎀 NAME 🎀

std::chrono::month::operator++, std::chrono::month::operator-- — bestie, these are the cute little in-place-arithmetic operators for std::chrono::month, straight out of the C++ Standard Libary man page 💅

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✨ SYNOPSIS ✨

constexpr std::chrono::month& operator++() noexcept;     (1) (since C++20)
constexpr std::chrono::month operator++( int ) noexcept; (2) (since C++20)
constexpr std::chrono::month& operator--() noexcept;     (3) (since C++20)
constexpr std::chrono::month operator--( int ) noexcept; (4) (since C++20)

okay so what these do is add or subtract 1 from the month value, and then reduce the result modulo 12 so it lands on an integer in the range [1, 12]. no cap, it just wraps around like a lil calendar loop 🦋

1. and 2) perform *this += std::chrono::months{1};.
2. and 4) perform *this -= std::chrono::months{1};.

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💖 PARAMETERS 💖

(none) — literally nothing, not a single argument, she takes no notes 🙈

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🌸 RETURN VALUE 🌸

• 1, 3) a reference to this month after modification 👑
• 2, 4) a copy of the month made before the modification, like a lil before-photo 📸

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🦋 NOTES 🦋

after a call to one of these functions, ok() is always true. yes bestie, always. she's that reliable 💀✨

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🍓 EXAMPLE 🍓

// Run this code

#include <cassert>
#include <chrono>
#include <iostream>

int main()
{
    std::chrono::month m{6};

    ++m;
    assert(m == std::chrono::month(7));

    --m;
    assert(m == std::chrono::month(6));

    m = std::chrono::December;
    m++; // rounds up to January
    assert(m.ok());
    std::cout << unsigned(m) << '\n';

    m = std::chrono::January;
    m--; // rounds down to December
    assert(m.ok());
    std::cout << unsigned(m) << '\n';
}

⭐ Output

1
12

see how December rounds up to January and January rounds down to December?? that wrap-around is genuinely iconic, main character energy fr fr 🔥

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🌈 SEE ALSO 🌈

• operator+= — adds or subtracts a number of months
• operator-= — (public member function)
• operator+ — performs arithmetic on months
• operator- — (function)
• and yeah, all of this is (C++20) era 💜

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mwah 💋 this page came from cppreference.com, dated 2024.06.10, and you're reading the std::chrono...::operator--(3) entry — go forth and increment your months, bestie 🫶✨