set_difference.hpp#

See Public API for a list of names and headers that are part of the public HPX API.

namespace hpx

Functions

template<typename ExPolicy, typename FwdIter1, typename FwdIter2, typename FwdIter3, typename Pred = detail::less> util::detail::algorithm_result<ExPolicy, FwdIter3>::type::type set_difference(ExPolicy &&policy, FwdIter1 first1, FwdIter1 last1, FwdIter2 first2, FwdIter2 last2, FwdIter3 dest, Pred &&op = Pred())#

Constructs a sorted range beginning at dest consisting of all elements present in the range [first1, last1) and not present in the range [first2, last2). This algorithm expects both input ranges to be sorted with the given binary predicate f.

Equivalent elements are treated individually, that is, if some element is found m times in [first1, last1) and n times in [first2, last2), it will be copied to dest exactly std::max(m-n, 0) times. The resulting range cannot overlap with either of the input ranges.

The resulting range cannot overlap with either of the input ranges.

The application of function objects in parallel algorithm invoked with a sequential execution policy object execute in sequential order in the calling thread (sequenced_policy) or in a single new thread spawned from the current thread (for sequenced_task_policy).

The application of function objects in parallel algorithm invoked with an execution policy object of type parallel_policy or parallel_task_policy are permitted to execute in an unordered fashion in unspecified threads, and indeterminately sequenced within each thread.

Note

Complexity: At most 2*(N1 + N2 - 1) comparisons, where N1 is the length of the first sequence and N2 is the length of the second sequence.

Template Parameters

ExPolicy – The type of the execution policy to use (deduced). It describes the manner in which the execution of the algorithm may be parallelized and the manner in which it applies user-provided function objects.
FwdIter1 – The type of the source iterators used (deduced) representing the first sequence. This iterator type must meet the requirements of an forward iterator.
FwdIter2 – The type of the source iterators used (deduced) representing the first sequence. This iterator type must meet the requirements of an forward iterator.
FwdIter3 – The type of the iterator representing the destination range (deduced). This iterator type must meet the requirements of an output iterator.
Pred – The type of an optional function/function object to use. Unlike its sequential form, the parallel overload of set_difference requires Pred to meet the requirements of CopyConstructible. This defaults to std::less<>

Parameters

policy – The execution policy to use for the scheduling of the iterations.
first1 – Refers to the beginning of the sequence of elements of the first range the algorithm will be applied to.
last1 – Refers to the end of the sequence of elements of the first range the algorithm will be applied to.
first2 – Refers to the beginning of the sequence of elements of the second range the algorithm will be applied to.
last2 – Refers to the end of the sequence of elements of the second range the algorithm will be applied to.
dest – Refers to the beginning of the destination range.
op – The binary predicate which returns true if the elements should be treated as equal. The signature of the predicate function should be equivalent to the following:
```
bool pred(const Type1 &a, const Type1 &b);
```
The signature does not need to have const &, but the function must not modify the objects passed to it. The type Type1 must be such that objects of type InIter can be dereferenced and then implicitly converted to Type1

Returns

The set_difference algorithm returns a hpx::future<FwdIter3> if the execution policy is of type sequenced_task_policy or parallel_task_policy and returns FwdIter3 otherwise. The set_difference algorithm returns the output iterator to the element in the destination range, one past the last element copied.