| | x is singular |
| Dereference | *x | x is dereferenceable | | |
| Dereference assignment | *x = t | x is dereferenceable | | *x is a copy of t |
| Member access | x->m | x is dereferenceable | Equivalent to (*x).m | |
Complexity guarantees The complexity of operations on trivial iterators is guaranteed to be amortized constant time.
Invariants | Identity | x == y if and only if &*x == &*y |
Models • A pointer to an object that is not part of an array.
Notes [1] The requirement for the return type of *x is specified as 'convertible to T', rather than simply T, because it sometimes makes sense for an iterator to return some sort of proxy object instead of the object that the iterator conceptually points to. Proxy objects are implementation details rather than part of an interface (one use of them, for example, is to allow an iterator to behave differently depending on whether its value is being read or written), so the value type of an iterator that returns a proxy is still T.
[2] Defining operator-> for iterators depends on a feature that is part of the C++ language but that is not yet implemented by all C++ compilers. If your compiler does not yet support this feature, the workaround is to use (*it).m instead of it->m.
See also Input Iterator, Output Iterator, Forward Iterator, Bidirectional Iterator, Random Access Iterator, Iterator Overview
Category: iterators
Component type: concept
Description An Input Iterator is an iterator that may be dereferenced to refer to some object, and that may be incremented to obtain the next iterator in a sequence. Input Iterators are not required to be mutable.
Refinement of Trivial iterator.
Associated types | Value type | The type of the value obtained by dereferencing an Input Iterator |
| Distance type | A signed integral type used to represent the distance from one iterator to another, or the number of elements in a range. |
Notation X A type that is a model of Input Iterator
T The value type of X
i, j Object of type X
t Object of type T
Definitions An iterator is past-the-end if it points beyond the last element of a container. Past-the-end values are nonsingular and nondereferenceable.
An iterator is valid if it is dereferenceable or past-the-end.
An iterator i is incrementable if there is a 'next' iterator, that is, if ++i is well-defined. Past-the-end iterators are not incrementable.
An Input Iterator j is reachable from an Input Iterator i if, after applying operator++ to i a finite number of times, i == j. [1]
The notation [i,j) refers to a range of iterators beginning with i and up to but not including j.
The range [i,j) is a valid range if both i and j are valid iterators, and j is reachable from i [2].
Valid expressions In addition to the expressions defined in Trivial Iterator, the following expressions must be valid.
