Random Access IteratorA Random Access Iterator is a Bidirectional Iterator that provides constant-time methods for moving forward and backward on a sequence in arbitrary-sized steps.
Random Access Iterator defines two new expressions and refines the ones described in Bidirectional Iterator.
| Expression | Expression type |
|---|---|
typename i::next | A model of Random Access Iterator |
typename i::prior | A model of Random Access Iterator |
typename i::template advance<n>::type | A model of Random Access Iterator |
typename i::template distance<j>::type | A model of Integral Constant |
Semantics of an expression is defined only where it is not defined in Bidirectional Iterator.
| Expression | Complexity | Precondition | Semantics | Postcondition |
|---|---|---|---|---|
typename i::template advance<n>::type | Amortized constant time | Including i itself, there must be n::value dereferenceable or past-the-end iterators following or preceding i, depending on whether n is positive or negative. | If n::value > 0, equivalent to executing i::next n::value times; if n::value < 0, equivalent to executing i::prior n::value times; if n::value == 0, this is a null operation [1]. | The resulting iterator is dereferenceable or past-the-end. |
typename i::template distance<j>::type | Amortized constant time | Either i is reachable from j or j is reachable from i, or both. | Returns an integral constant n such that i::template advance<n>::type is identical to j. |
For any random access iterators i and j the following invariants always hold:
i::advance<n>::type is well-defined, then i::advance<n>::type::advance< negate<n>::type >::type is a null operation.
Random Access Sequence, Bidirectional Iterator