std::revers...,+=,--,-,-=(3)

💖 NAME 💖

okay so bestie, welcome to the std::revers...,+=,--,-,-=(3) page from the C++ Standard Libary manual — yes, that spelling is what the header says, we're keeping it. The NAME bit is literally:

std::reverse_iterator::operator++,+,+=,--,-,-= -
std::reverse_iterator::operator++,+,+=,--,-,-=

so yeah, it's the whole operator crew for std::reverse_iterator: increment, decrement, plus, minus, plus-equals, minus-equals. iconic behavior, no cap. 💅

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✨ Synopsis ✨

the manpage formatting turned this synopsis into a little chaos gremlin, but every overload and every (until C++17) / (since C++17) is still here, untouched:

reverse_iterator&          (until
operator++();              C++17)
constexpr                  (since
reverse_iterator&          C++17)
operator++();
reverse_iterator&                  (until
operator--();                      C++17)
constexpr                          (since
reverse_iterator&                  C++17)
operator--();
reverse_iterator                           (until
operator++( int );                         C++17)
constexpr                                  (since
reverse_iterator                           C++17)
operator++( int );
reverse_iterator                                  (until
operator--( int );                                C++17)
constexpr                                         (since
reverse_iterator                                  C++17)
operator--( int );
reverse_iterator
operator+(                                               (until
difference_type n                                        C++17)
) const;
constexpr
reverse_iterator                                         (since
operator+(                                               C++17)
difference_type n  (1)
) const;
reverse_iterator
operator-(             (2)
(until
difference_type n
C++17)
) const;                   (3)
constexpr
reverse_iterator
(since
operator-(                         (4)
C++17)
difference_type n
) const;                                   (5)
reverse_iterator&
operator+=(
(until
difference_type n
C++17)
);
constexpr                                         (6)
reverse_iterator&
(since
operator+=(
C++17)
difference_type n
);                                                       (7)
reverse_iterator&
operator-=(
(until
difference_type n
C++17)
);
constexpr                                                       (8)
reverse_iterator&
(since
operator-=(
C++17)
difference_type n
);

Increments or decrements the iterator. Inverse operations are applied to the underlying operator because of the reverse order. 🌀

• 1,2) Pre-increments or pre-decrements by one respectively.
• 3,4) Post-increments or post-decrements by one respectively.
• 5,6) Returns an iterator which is advanced by n or -n positions respectively.
• 7,8) Advances the iterator by n or -n positions respectively.

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🌸 Parameters 🌸

• n — position relative to current location.

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🎀 Return value 🎀

• 1,2) *this
• 3,4) A copy of *this that was made before the change.
• 5,6) reverse_iterator(base()-n) or reverse_iterator(base()+n) respectively.
• 7,8) *this

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🦋 Example 🦋

// Run this code

#include <iostream>
#include <iterator>
#include <list>
#include <vector>

int main()
{
    std::vector v{0, 1, 2, 3, 4};
    auto rv = std::reverse_iterator{v.rbegin()};
    std::cout << *(++rv) << ' '; // 3
    std::cout << *(--rv) << ' '; // 4
    std::cout << *(rv + 3) << ' '; // 1
    rv += 3;
    std::cout << rv[0] << ' '; // 1
    rv -= 3;
    std::cout << rv[0] << '\n'; // 4

    std::list l{5, 6, 7, 8};
    auto rl = std::reverse_iterator{l.rbegin()};
    std::cout << *(++rl) << ' '; // OK: 3
    std::cout << *(--rl) << '\n'; // OK: 4
    // The following statements raise compilation error because the
    // underlying iterator does not model the random access iterator:
//  *(rl + 3) = 13;
//  rl += 3;
//  rl -= 3;
}

and bestie, those last commented-out lines are not a cute little suggestion — they raise compilation error because the underlying iterator does not model the random access iterator. leave them commented, fr fr. 😭

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🌈 Output 🌈

3 4 1 1 4
7 8

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👑 See also 👑

• operator+ advances the iterator — function template
• operator- computes the distance between two iterator adaptors — function template

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mwah 💋 this page came from http://cppreference.com, and the version/date stamped on it is 2024.06.10. slay. ✨