C++ concepts: Iterator
From cppreference.com
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
- The type
It
satisfiesCopyConstructible
, and - The type
It
satisfiesCopyAssignable
, and - The type
It
satisfiesDestructible
, and - lvalues of type
It
satisfySwappable
, and
Given
-
r
, an lvalue of typeIt
, -
reference
, the type denoted by std::iterator_traits<It>::reference
The following expressions must be valid and have their specified effects:
Expression | Return Type | Precondition |
---|---|---|
*r | unspecified |
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.
Iterator
s 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.