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C++ concepts: Iterator

From cppreference.com
< cpp‎ | concept

The Iterator concept describes types that can be used to identify and traverse the elements of a container.

Iterator is the base concept used by other iterator types: InputIterator, OutputIterator, ForwardIterator, BidirectionalIterator, and RandomAccessIterator. Iterators can be thought of as an abstraction of pointers.

[edit] Requirements

The type It satisfies Iterator if

Given

The following expressions must be valid and have their specified effects:

Expression Return Type Precondition
*r reference r is dereferenceable (see below)
++r It& r is incrementable (see below)

[edit] Dereferenceable iterators

Iterators for which the behavior of the expression *i is defined are called dereferenceable.

Iterators are not dereferenceable if

  • they are past-the-end iterators (including pointers past the end of an array) or before-begin iterators. Such iterators may be dereferenceable in a particular implementation, but the library never assumes that they are.
  • they are singular iterators, that is, iterators that are not associated with any sequence. A null pointer, as well as a default-constructed pointer (holding an indeterminate value) is singular
  • they were invalidated by one of the iterator-invalidating operations on the sequence to which they refer.

Iterators for which the behavior of the expression ++i is defined are called incrementable.

[edit] See also