NAME¶

std::experimental::ranges::RandomAccessIterator - std::experimental::ranges::RandomAccessIterator

Synopsis¶

Defined in header <experimental/ranges/iterator>
template <class I>

concept bool RandomAccessIterator =
BidirectionalIterator<I> &&
DerivedFrom<ranges::iterator_category_t<I>,
ranges::random_access_iterator_tag> &&
StrictTotallyOrdered<I> &&
SizedSentinel<I, I> &&
requires(I i, const I j, const ranges::difference_type_t<I> n) { (ranges TS)
{ i += n } -> Same<I>&;
{ j + n } -> Same<I>&&;
{ n + j } -> Same<I>&&;
{ i -= n } -> Same<I>&;
{ j - n } -> Same<I>&&;
j[n];
requires Same<decltype(j[n]), ranges::reference_t<I>>;

};

The concept RandomAccessIterator<I> refines BidirectionalIterator by adding support
for constant time advancement with the +=, +, -=, and - operators, constant time
computation of distance with -, and array notation with subscripting.

Let a and b be valid iterators of type I such that b is reachable from a, and let n
be a value of type ranges::difference_type_t<I> equal to b - a.
RandomAccessIterator<I> is satisfied only if:

* (a += n) is equal to b.
* std::addressof(a += n) is equal to std::addressof(a).
* (a + n) is equal to (a += n).
* (a + n) is equal to (n + a).
* For any two positive integers x and y, if a + (x + y) is valid, then a + (x + y)
is equal to (a + x) + y.
* a + 0 is equal to a.
* If (a + (n - 1)) is valid, then --b is equal to (a + (n - 1)).
* (b += -n) and (b -= n) are both equal to a.
* std::addressof(b -= n) is equal to std::addressof(b).
* (b - n) is equal to (b -= n).
* If b is dereferenceable, then a[n] is valid and is equal to *b.
* bool(a <= b) is true .

Equality preservation

An expression is equality preserving if it results in equal outputs given equal
inputs.

* The inputs to an expression consist of its operands.
* The outputs of an expression consist of its result and all operands modified by
the expression (if any).

Every expression required to be equality preserving is further required to be
stable: two evaluations of such an expression with the same input objects must have
equal outputs absent any explicit intervening modification of those input objects.

Unless noted otherwise, every expression used in a requires-expression is required
to be equality preserving and stable, and the evaluation of the expression may only
modify its non-constant operands. Operands that are constant must not be modified.

Implicit expression variations

A requires-expression that uses an expression that is non-modifying for some
constant lvalue operand also implicitly requires additional variations of that
expression that accept a non-constant lvalue or (possibly constant) rvalue for the
given operand unless such an expression variation is explicitly required with
differing semantics. These implicit expression variations must meet the same
semantic requirements of the declared expression. The extent to which an
implementation validates the syntax of the variations is unspecified.