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1431. is_permutation must be more restrictive

Section: 26.6.14 [alg.is.permutation] Status: C++11 Submitter: INCITS Opened: 2010-08-25 Last modified: 2021-06-06

Priority: Not Prioritized

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Discussion:

Addresses US-120

is_permutation is underspecified for anything but the simple case where both ranges have the same value type and the comparison function is an equivalence relation.

[ Resolved in Rapperswil by a motion to directly apply the words from the ballot comment in N3102. ]

Proposed resolution:

Restrict is_permutation to the case where it is well specified. See Appendix 1 - Additional Details