[header][other] iterator

*[header][other] iterator

<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:

• InputOutput
• Forward
• Bidirectional
• Random Access

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:

category				properties	valid expressions
all categories				copy-constructible, copy-assignable and destructible	X b(a); b = a;
				Can be incremented	++a a++
Random Access	Bidirectional	Forward	Input	Supports equality/inequality comparisons	a == b a != b
				Can be dereferenced as an rvalue	*a a->m
			Output	Can be dereferenced as an lvalue  (only for mutable iterator types)	*a = t *a++ = t
				default-constructible	X 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 iterators	a < 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:

advance

Advance iterator (function template )

distance

Return distance between iterators (function template )

begin 

Iterator to beginning (function template )

end 

Iterator to end (function template )

prev 

Get iterator to previous element (function template )

next 

Get iterator to next element (function template )

Iterator generators:

back_inserter

Construct back insert iterator (function template )

front_inserter

Constructs front insert iterator (function template )

inserter

Construct insert iterator (function template )

make_move_iterator 

Construct move iterator (function template )

Classes

iterator

Iterator base class (class template )

iterator_traits

Iterator traits (class template )

Predefined iterators

reverse_iterator

Reverse iterator (class template )

move_iterator 

Move iterator (class template )

back_insert_iterator

Back insert iterator (class template )

front_insert_iterator

Front insert iterator (class template )

insert_iterator

Insert iterator (class template )

istream_iterator

Istream iterator (class template )

ostream_iterator

Ostream iterator (class template )

istreambuf_iterator

Input stream buffer iterator (class template )

ostreambuf_iterator

Output stream buffer iterator (class template )

Category tags

input_iterator_tag

Input iterator category (class )

output_iterator_tag

Output iterator category (class )

forward_iterator_tag

Forward iterator category (class )

bidirectional_iterator_tag

Bidirectional iterator category (class )

random_access_iterator_tag

Random-access iterator category (class )

내용 출처 : http://www.cplusplus.com/reference/iterator/