C++ named requirements: LegacyRandomAccessIterator

A LegacyRandomAccessIterator is a LegacyBidirectionalIterator that can be moved to point to any element in constant time.

A pointer to an element of an array satisfies all requirements of LegacyRandomAccessIterator.

Requirements

The type It satisfies LegacyRandomAccessIterator if.

The type It satisfies LegacyBidirectionalIterator

And, given.

value_type, the type denoted by std::iterator_traits<It>::value_type
difference_type, the type denoted by std::iterator_traits<It>::difference_type
reference, the type denoted by std::iterator_traits<It>::reference
i, a, b, objects of type It or const It
r, a value of type It&
n, an integer of type difference_type

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

Expression	Return type	Operational semantics	Notes
`r += n`	`It&`	`difference_type m = n; if (m >= 0) while (m--) ++r; else while (m++) --r; return r;`	`n` can be both positive or negative The complexity is constant (that is, the implementation cannot actually execute the while loop shown in operational semantics)
`a + n` `n + a`.	`It`	`It temp = a; return temp += n;`	`n` can be both positive or negative `a + n == n + a`
`r -= n`	`It&`	`return r += -n;`	The absolute value of `n` must be within the range of representable values of `difference_type`.
`i - n`	`It`	`It temp = i; return temp -= n;`
`b - a`	`difference_type`	`return n;`	Precondition: there exists a value `n` of type `difference_type` such that `a+n==b` Postcondition: `b == a + (b - a)`.
`i[n]`	convertible to `reference`	`*(i + n)`
`a < b`	contextually convertible to `bool`	`b - a > 0`	Strict total ordering relation: `!(a < a)` if `a < b` then `!(b < a)` if `a < b` and `b < c` then `a < c` `a < b` or `b < a` or `a == b` (exactly one of the expressions is true)
`a > b`	contextually convertible to `bool`	`b < a`	Total ordering relation opposite to `a < b`
`a >= b`	contextually convertible to `bool`	`!(a < b)`
`a <= b`	contextually convertible to `bool`	`!(a > b)`

The above rules imply that LegacyRandomAccessIterator also implements LessThanComparable.

A mutable LegacyRandomAccessIterator is a LegacyRandomAccessIterator that additionally satisfies the LegacyOutputIterator requirements.

Concept

For the definition of std::iterator_traits, the following exposition-only concept is defined.

template<class I>
concept __LegacyRandomAccessIterator =
  __LegacyBidirectionalIterator<I> && std::StrictTotallyOrdered<I> &&
  requires(I i, typename std::incrementable_traits<I>::difference_type n) {
    { i += n } -> std::Same<I&>;
    { i -= n } -> std::Same<I&>;
    { i +  n } -> std::Same<I>;
    { n +  i } -> std::Same<I>;
    { i -  n } -> std::Same<I>;
    { i -  i } -> std::Same<decltype(n)>;
    {  i[n]  } -> std::iter_reference_t<I>;
  };

where the exposition-only concept __LegacyBidirectionalIterator is described in LegacyBidirectionalIterator#Concept.

(since C++20)

C++ named requirements: LegacyRandomAccessIterator

Requirements

Concept

See also