[section:inplace_merge inplace_merge]

[heading Prototype]

``
template<class BidirectionalRange>
BidirectionalRange&
inplace_merge( BidirectionalRange& rng,
               typename range_iterator<BidirectionalRange>::type middle );

template<class BidirectionalRange>
const BidirectionalRange&
inplace_merge( const BidirectionalRange& rng,
               typename range_iterator<const BidirectionalRange>::type middle );

template<class BidirectionalRange, class BinaryPredicate>
BidirectionalRange&
inplace_merge( BidirectionalRange& rng,
               typename range_iterator<BidirectionalRange>::type middle,
               BinaryPredicate pred );

template<class BidirectionalRange, class BinaryPredicate>
const BidirectionalRange&
inplace_merge( const BidirectionalRange& rng,
               typename range_iterator<const BidirectionalRange>::type middle,
               BinaryPredicate pred );
``

[heading Description]

`inplace_merge` combines two consecutive sorted ranges `[begin(rng), middle)` and `[middle, end(rng))` into a single sorted range `[begin(rng), end(rng))`. That is, it starts with a range `[begin(rng), end(rng))` that consists of two pieces each of which is in ascending order, and rearranges it so that the entire range is in ascending order. `inplace_merge` is stable, meaning both that the relative order of elements within each input range is preserved.

[heading Definition]

Defined in the header file `boost/range/algorithm/inplace_merge.hpp`

[heading Requirements]

[*For the non-predicate version:]

* `BidirectionalRange` is a model of the __bidirectional_range__ Concept.
* `BidirectionalRange` is mutable.
* `range_value<BidirectionalRange>::type` is a model of `LessThanComparableConcept`
* The ordering on objects of `range_type<BidirectionalRange>::type` is a [*/strict weak ordering/], as defined in the `LessThanComparableConcept` requirements.

[*For the predicate version:]
* `BidirectionalRange` is a model of the __bidirectional_range__ Concept.
* `BidirectionalRange` is mutable.
* `BinaryPredicate` is a model of the `StrictWeakOrderingConcept`.
* `BidirectionalRange`'s value type is convertible to both `BinaryPredicate`'s argument types.

[heading Precondition:]

[heading For the non-predicate version:]

* `middle` is in the range `rng`.
* `[begin(rng), middle)` is in ascending order. That is for each pair of adjacent elements `[x,y]`, `y < x` is `false`.
* `[middle, end(rng))` is in ascending order. That is for each pair of adjacent elements `[x,y]`, `y < x` is `false`.

[heading For the predicate version:]

* `middle` is in the range `rng`.
* `[begin(rng), middle)` is in ascending order. That is for each pair of adjacent elements `[x,y]`, `pred(y,x) == false`.
* `[middle, end(rng))` is in ascending order. That is for each pair of adjacent elements `[x,y]`, `pred(y,x) == false`.

[heading Complexity]

Worst case: `O(N log(N))`

[endsect]