---
name: "std::reverse_iterator"
section: "3cxx"
platform: "linux"
package: "libstdc++-12-doc"
version: "12.4.0-5"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/std::reverse_iterator/3cxx"
---

# std::reverse\_iterator(3cxx)

## NAME

std::reverse\_iterator\< \_Iterator \>

## SYNOPSIS

`#include <iterator>`

Inherits **std::iterator\< iterator\_traits\< \_Iterator \>::iterator\_category, iterator\_traits\< \_Iterator \>::value\_type, iterator\_traits\< \_Iterator \>::difference\_type, iterator\_traits\< \_Iterator \>::pointer, iterator\_traits\< \_Iterator \>::reference \>**.

### Public Types

**using** **difference\_type** = iter\_difference\_t\< \_Iterator \>\
 **using** **iterator\_category** = **\_\_detail::\_\_clamp\_iter\_cat**\< **typename** \_\_traits\_type::iterator\_category, **random\_access\_iterator\_tag** \>\
 **using** **iterator\_concept** = \_\_conditional\_t\< random\_access\_iterator\< \_Iterator \>, **random\_access\_iterator\_tag**, **bidirectional\_iterator\_tag** \>\
 **typedef** \_Iterator **iterator\_type**\
 **typedef** \_\_traits\_type::pointer **pointer**\
 **using** **reference** = iter\_reference\_t\< \_Iterator \>\
 **using** **value\_type** = iter\_value\_t\< \_Iterator \>\

### Public Member Functions

constexpr **reverse\_iterator** () noexcept(/\***conditional** \*/)\
 constexpr **reverse\_iterator** (const **reverse\_iterator** &\_\_x) noexcept(/\***conditional** \*/)\
 template\<**typename** \_Iter \> \
 requires \_\_convertible\<\_Iter\>constexpr **reverse\_iterator** (const **reverse\_iterator**\< \_Iter \> &\_\_x) noexcept(/\***conditional** \*/)"\
 constexpr **reverse\_iterator** (iterator\_type \_\_x) noexcept(/\***conditional** \*/)\
 constexpr iterator\_type **base** () const noexcept(/\***conditional** \*/)\
 constexpr **reference** **operator\*** () const\
 constexpr **reverse\_iterator** **operator+** (**difference\_type** \_\_n) const\
 constexpr **reverse\_iterator** & **operator++** ()\
 constexpr **reverse\_iterator** **operator++** (int)\
 constexpr **reverse\_iterator** & **operator+=** (**difference\_type** \_\_n)\
 constexpr **reverse\_iterator** **operator-** (**difference\_type** \_\_n) const\
 constexpr **reverse\_iterator** & **operator--** ()\
 constexpr **reverse\_iterator** **operator--** (int)\
 constexpr **reverse\_iterator** & **operator-=** (**difference\_type** \_\_n)\
 constexpr pointer **operator-\>** () const\
 **reverse\_iterator** & **operator=** (const **reverse\_iterator** &)=**default**\
 template\<**typename** \_Iter \> \
 requires \_\_convertible\<\_Iter\> && assignable\_from\<\_Iterator&, const \_Iter&\>constexpr **reverse\_iterator** & **operator=** (const **reverse\_iterator**\< \_Iter \> &\_\_x) noexcept(/\***conditional** \*/)"\
 constexpr **reference** **operator\[\]** (**difference\_type** \_\_n) const\

### Protected Types

**typedef** **iterator\_traits**\< \_Iterator \> **\_\_traits\_type**\

### Protected Attributes

\_Iterator **current**\

### Friends

constexpr iter\_rvalue\_reference\_t\< \_Iterator \> **iter\_move** (const **reverse\_iterator** &\_\_i) noexcept(is\_nothrow\_copy\_constructible\_v\< \_Iterator \> &&noexcept(ranges::iter\_move(--**std::declval**\< \_Iterator & \>())))\
 template\<indirectly\_swappable\< \_Iterator \> \_Iter2\> constexpr **void** **iter\_swap** (const **reverse\_iterator** &\_\_x, const **reverse\_iterator**\< \_Iter2 \> &\_\_y) noexcept(is\_nothrow\_copy\_constructible\_v\< \_Iterator \> &&is\_nothrow\_copy\_constructible\_v\< \_Iter2 \> &&noexcept(ranges::iter\_swap(--**std::declval**\< \_Iterator & \>(), --**std::declval**\< \_Iter2 & \>())))\

## Detailed Description

### template\<typename \_Iterator\>

class std::reverse\_iterator\< \_Iterator \>"Bidirectional and random access iterators have corresponding reverse iterator adaptors that iterate through the data structure in the opposite direction. They have the same signatures as the corresponding iterators. The fundamental relation between a reverse iterator and its corresponding iterator `i` is established by the identity:

```
&*(reverse_iterator(i)) == &*(i - 1)
```

*This mapping is dictated by the fact that while there is always a pointer past the end of an array, there might not be a valid pointer before the beginning of an array.* \[24.4.1\]/1,2

Reverse iterators can be tricky and surprising at first. Their semantics make sense, however, and the trickiness is a side effect of the requirement that the iterators must be safe.

## Constructor & Destructor Documentation

### template\<typename \_Iterator \> constexpr std::reverse\_iterator\< \_Iterator \>::reverse\_iterator ()` [inline]`, ` [constexpr]`, ` [noexcept]`

The default constructor value-initializes member `current`. If it is a pointer, that means it is zero-initialized.

### template\<typename \_Iterator \> constexpr std::reverse\_iterator\< \_Iterator \>::reverse\_iterator (iterator\_type \_\_x)` [inline]`, ` [explicit]`, ` [constexpr]`, ` [noexcept]`

This iterator will move in the opposite direction that `x` does.

### template\<typename \_Iterator \> constexpr std::reverse\_iterator\< \_Iterator \>::reverse\_iterator (const reverse\_iterator\< \_Iterator \> & \_\_x)` [inline]`, ` [constexpr]`, ` [noexcept]`

The copy constructor is normal.

### template\<typename \_Iterator \> template\<typename \_Iter \>

requires \_\_convertible\<\_Iter\>constexpr **std::reverse\_iterator**\< \_Iterator \>::reverse\_iterator (const **reverse\_iterator**\< \_Iter \> & \_\_x)` [inline]`, ` [constexpr]`, ` [noexcept]`" A reverse\_iterator across other types can be copied if the underlying iterator can be converted to the type of `current`.

## Member Function Documentation

### template\<typename \_Iterator \> constexpr iterator\_type std::reverse\_iterator\< \_Iterator \>::base () const` [inline]`, ` [constexpr]`, ` [noexcept]`

**Returns**

`current`, the iterator used for underlying work.

### template\<typename \_Iterator \> constexpr reference std::reverse\_iterator\< \_Iterator \>::operator\* () const` [inline]`, ` [constexpr]`

**Returns**

A reference to the value at `--current`

This requires that `--current` is dereferenceable.

**Warning**

This implementation requires that for an iterator of the underlying iterator type, `x`, a reference obtained by `*x` remains valid after `x` has been modified or destroyed. This is a bug: http://gcc.gnu.org/PR51823

### template\<typename \_Iterator \> constexpr reverse\_iterator std::reverse\_iterator\< \_Iterator \>::operator+ (difference\_type \_\_n) const` [inline]`, ` [constexpr]`

**Returns**

A reverse\_iterator that refers to `current` - *\_\_n*

The underlying iterator must be a Random Access Iterator.

### template\<typename \_Iterator \> constexpr reverse\_iterator & std::reverse\_iterator\< \_Iterator \>::operator++ ()` [inline]`, ` [constexpr]`

**Returns**

`*this`

Decrements the underlying iterator.

### template\<typename \_Iterator \> constexpr reverse\_iterator std::reverse\_iterator\< \_Iterator \>::operator++ (int)` [inline]`, ` [constexpr]`

**Returns**

The original value of `*this`

Decrements the underlying iterator.

### template\<typename \_Iterator \> constexpr reverse\_iterator & std::reverse\_iterator\< \_Iterator \>::operator+= (difference\_type \_\_n)` [inline]`, ` [constexpr]`

**Returns**

\*this

Moves the underlying iterator backwards *\_\_n* steps. The underlying iterator must be a Random Access Iterator.

### template\<typename \_Iterator \> constexpr reverse\_iterator std::reverse\_iterator\< \_Iterator \>::operator- (difference\_type \_\_n) const` [inline]`, ` [constexpr]`

**Returns**

A reverse\_iterator that refers to `current` - *\_\_n*

The underlying iterator must be a Random Access Iterator.

### template\<typename \_Iterator \> constexpr reverse\_iterator & std::reverse\_iterator\< \_Iterator \>::operator-- ()` [inline]`, ` [constexpr]`

**Returns**

`*this`

Increments the underlying iterator.

### template\<typename \_Iterator \> constexpr reverse\_iterator std::reverse\_iterator\< \_Iterator \>::operator-- (int)` [inline]`, ` [constexpr]`

**Returns**

A reverse\_iterator with the previous value of `*this`

Increments the underlying iterator.

### template\<typename \_Iterator \> constexpr reverse\_iterator & std::reverse\_iterator\< \_Iterator \>::operator-= (difference\_type \_\_n)` [inline]`, ` [constexpr]`

**Returns**

\*this

Moves the underlying iterator forwards *\_\_n* steps. The underlying iterator must be a Random Access Iterator.

### template\<typename \_Iterator \> constexpr pointer std::reverse\_iterator\< \_Iterator \>::operator-\> () const` [inline]`, ` [constexpr]`

**Returns**

A pointer to the value at `--current`

This requires that `--current` is dereferenceable.

### template\<typename \_Iterator \> constexpr reference std::reverse\_iterator\< \_Iterator \>::operator\[\] (difference\_type \_\_n) const` [inline]`, ` [constexpr]`

**Returns**

The value at `current` - *\_\_n* - 1

The underlying iterator must be a Random Access Iterator.

## Author

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