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1039. Sequence container back function should also support const_iterator

Section: 23.2.4 [sequence.reqmts] Status: C++11 Submitter: Alisdair Meredith Opened: 2009-03-12 Last modified: 2016-01-28

Priority: Not Prioritized

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Discussion:

Addresses UK 234 [CD1]

The reference to iterator in semantics for back should also allow for const_iterator when called on a const-qualified container. This would be ugly to specify in the 03 standard, but is quite easy with the addition of auto in this new standard.

[ Summit: ]

Agree.

[ Batavia (2009-05): ]

We agree with the proposed resolution. Move to Tentatively Ready.

Proposed resolution:

In 23.2.4 [sequence.reqmts] Table 84, replace iterator with auto in semantics for back:

Table 84 — Optional sequence container operations

Expression	Return type	Operational semantics	Container
a.back()	reference; const_reference for constant a	{ iterator auto tmp = a.end(); --tmp; return *tmp; }	vector, list, deque, basic_string