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- [/
- Copyright 2010 Neil Groves
- Distributed under the Boost Software License, Version 1.0.
- (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
- /]
- [section:prev_permutation prev_permutation]
- [heading Prototype]
- ``
- template<class BidirectionalRange>
- bool prev_permutation(BidirectionalRange& rng);
- template<class BidirectionalRange>
- bool prev_permutation(const BidirectionalRange& rng);
- template<class BidirectionalRange, class Compare>
- bool prev_permutation(BidirectionalRange& rng, Compare pred);
- template<class BidirectionalRange, class Compare>
- bool prev_permutation(const BidirectionalRange& rng, Compare pred);
- ``
- [heading Description]
- `prev_permutation` transforms the range of elements `rng` into the lexicographically next smaller permutation of the elements if such a permutation exists. If one does not exist then the range is transformed into the lexicographically largest permutation and `false` is returned. `true` is returned when the next smaller permutation is successfully generated.
- The ordering relationship is determined by using `operator<` in the non-predicate versions, and by evaluating `pred` in the predicate versions.
- [heading Definition]
- Defined in the header file `boost/range/algorithm/permutation.hpp`
- [heading Requirements]
- [*For the non-predicate versions:]
- * `BidirectionalRange` is a model of the __bidirectional_range__ Concept.
- * `BidirectionalRange` is mutable.
- * `BidirectionalRange`'s value type is a model of the `LessThanComparableConcept`.
- * The ordering of objects of type `BidirectionalRange`'s value type is a [*/strict weak ordering/], as defined in the `LessThanComparableConcept` requirements.
- [*For the predicate versions:]
- * `BidirectionalRange` is a model of the __bidirectional_range__ Concept.
- * `BidirectionalRange` is mutable.
- * `Compare` is a model of the `StrictWeakOrderingConcept`.
- * `BidirectionalRange`'s value type is convertible to both of `Compare`'s argument types.
- [heading Complexity]
- Linear. At most `distance(rng) / 2` swaps.
- [endsect]
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