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### 1210. Iterator reachability should not require a container

Section: 25.3 [iterator.requirements] Status: Resolved Submitter: Alisdair Meredith Opened: 2009-09-18 Last modified: 2016-01-28

Priority: Not Prioritized

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Discussion:

p6 Iterator requirements 25.3 [iterator.requirements]

> An iterator `j` is called reachable from an iterator `i` if and only if there is a finite sequence of applications of the expression `++i` that makes `i == j`. If `j` is reachable from `i`, they refer to the same container.

A good example would be stream iterators, which do not refer to a container. Typically, the end iterator from a range of stream iterators will compare equal for many such ranges. I suggest striking the second sentence.

An alternative wording might be:

> If `j` is reachable from `i`, and both `i` and `j` are dereferencable iterators, then they refer to the same range.

[ 2010 Pittsburgh: Moved to NAD Editorial Resolved. Rationale added below. ]

Rationale:

Solved by N3066.

Proposed resolution:

Change 25.3 [iterator.requirements], p6:

> An iterator `j` is called reachable from an iterator `i` if and only if there is a finite sequence of applications of the expression `++i` that makes `i == j`. If `j` is reachable from `i`, they refer to the same container.