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### 1039. Sequence container `back` function should also support `const_iterator`

Section: 24.2.4 [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 24.2.4 [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`