header

<iterator>

Iterator definitions
An iterator is any object that, pointing to some element in a range of elements (such as an array or a container), has the ability to iterate through the elements of that range using a set of operators (with at least the increment (++) and dereference (*) operators).

The most obvious form of iterator is a pointer: A pointer can point to elements in an array, and can iterate through them using the increment operator (++). But other kinds of iterators are possible. For example, each container type (such as a list) has a specific iterator type designed to iterate through its elements.

Notice that while a pointer is a form of iterator, not all iterators have the same functionality of pointers; Depending on the properties supported by iterators, they are classified into five different categories:

Iterator categories

Iterators are classified into five categories depending on the functionality they implement:


Input and output iterators are the most limited types of iterators: they can perform sequential single-pass input or output operations.

Forward iterators have all the functionality of input iterators and -if they are not constant iterators- also the functionality of output iterators, although they are limited to one direction in which to iterate through a range (forward). All standard containers support at least forward iterator types.

Bidirectional iterators are like forward iterators but can also be iterated through backwards.

Random-access iterators implement all the functionality of bidirectional iterators, and also have the ability to access ranges non-sequentially: distant elements can be accessed directly by applying an offset value to an iterator without iterating through all the elements in between. These iterators have a similar functionality to standard pointers (pointers are iterators of this category).

The properties of each iterator category are:

categorypropertiesvalid expressions
all categoriescopy-constructible, copy-assignable and destructibleX b(a);
b = a;
Can be incremented++a
a++
Random AccessBidirectionalForwardInputSupports equality/inequality comparisonsa == b
a != b
Can be dereferenced as an rvalue*a
a->m
OutputCan be dereferenced as an lvalue
(only for mutable iterator types)
*a = t
*a++ = t
default-constructibleX a;
X()
Multi-pass: neither dereferencing nor incrementing affects dereferenceability{ b=a; *a++; *b; }
Can be decremented--a
a--
*a--
Supports arithmetic operators + and -a + n
n + a
a - n
a - b
Supports inequality comparisons (<, >, <= and >=) between iteratorsa < b
a > b
a <= b
a >= b
Supports compound assignment operations += and -=a += n
a -= n
Supports offset dereference operator ([])a[n]

Where X is an iterator type, a and b are objects of this iterator type, t is an object of the type pointed by the iterator type, and n is an integer value.

For more details, see the references for input iterator, output iterator, forward iterator, bidirectional iterator and random-access iterator.

Functions

Iterator operations:

Iterator generators:

Classes


Predefined iterators


Category tags

<rt id="pwjBlLZ"><small id="pwjBlLZ"></small></rt>
<acronym id="pwjBlLZ"></acronym><rt id="pwjBlLZ"></rt>
<tr id="pwjBlLZ"><optgroup id="pwjBlLZ"></optgroup></tr><tr id="pwjBlLZ"><optgroup id="pwjBlLZ"></optgroup></tr><acronym id="pwjBlLZ"><small id="pwjBlLZ"></small></acronym>
<acronym id="pwjBlLZ"><optgroup id="pwjBlLZ"></optgroup></acronym>
<option id="pwjBlLZ"></option>
<tr id="pwjBlLZ"><optgroup id="pwjBlLZ"></optgroup></tr>
<acronym id="pwjBlLZ"><small id="pwjBlLZ"></small></acronym><acronym id="pwjBlLZ"></acronym>
<acronym id="pwjBlLZ"><small id="pwjBlLZ"></small></acronym>
  • 6512882421 2018-04-19
  • 4659652420 2018-04-19
  • 2967832419 2018-04-19
  • 8339042418 2018-04-19
  • 8147112417 2018-04-19
  • 2774752416 2018-04-19
  • 4316132415 2018-04-19
  • 6265742414 2018-04-19
  • 1875142413 2018-04-19
  • 4146552412 2018-04-19
  • 8205662411 2018-04-19
  • 959982410 2018-04-19
  • 7153742409 2018-04-19
  • 9349932408 2018-04-18
  • 6024052407 2018-04-18
  • 2113432406 2018-04-18
  • 7629172405 2018-04-18
  • 163882404 2018-04-18
  • 3515922403 2018-04-18
  • 5047802402 2018-04-18