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### 919. (`forward_`)`list` specialized remove algorithms are over constrained

Section: 99 [forwardlist.ops], 22.3.10.5 [list.ops] Status: NAD Submitter: Daniel Krügler Opened: 2008-10-06 Last modified: 2016-01-28

Priority: Not Prioritized

View all other issues in [forwardlist.ops].

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Discussion:

The signatures of `forwardlist::remove` and `list::remove` defined in 99 [forwardlist.ops] before 11 + 22.3.10.5 [list.ops] before 15:

>     requires EqualityComparable<T> void remove(const T& value);

are asymmetric to their predicate variants (which only require `Predicate`, not `EquivalenceRelation`) and with the free algorithm remove (which only require `HasEqualTo`). Also, nothing in the pre-concept WP N2723 implies that `EqualityComparable` should be the intended requirement.

[ Batavia (2009-05): ]

> We agree with the proposed resolution, but would like additional input from concepts experts.

> Move to Review.

[ 2009-07-21 Alisdair adds: ]

> Current rationale and wording for this issue is built around concepts. I suggest the issue reverts to Open status. I believe there is enough of an issue to review after concepts are removed from the WP to re-examine the issue in Santa Cruz, rather than resolve as NAD Concepts.

[ 2009-10-10 Daniel adds: ]

> Recommend NAD: The concept-free wording as of N2960 has no longer the over-specified requirement `EqualityComparable` for the remove function that uses `==`. In fact, now the same test conditions exists as for the free algorithm `remove` (25.7.8 [alg.remove]). The error was introduced in the process of conceptifying.

[ 2009-10 Santa Cruz: ]

> NAD, solved by the removal of concepts.

Proposed resolution:

1. Replace in 99 [forwardlist.ops] before 11 and in 22.3.10.5 [list.ops] before 15

   >     requires EqualityComparable<T> HasEqualTo<T, T> void remove(const T& value);