for_each.hpp#

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

namespace hpx

Functions

template<typename InIter, typename F> F for_each(InIter first, InIter last, F &&f)#

Applies f to the result of dereferencing every iterator in the range [first, last).

If f returns a result, the result is ignored.

If the type of first satisfies the requirements of a mutable iterator, f may apply non-constant functions through the dereferenced iterator.

Note

Complexity: Applies f exactly last - first times.

Template Parameters

InIter – The type of the source begin and end iterator used (deduced). This iterator type must meet the requirements of an input iterator.
F – The type of the function/function object to use (deduced). F must meet requirements of MoveConstructible.

Parameters

first – Refers to the beginning of the sequence of elements the algorithm will be applied to.
last – Refers to the end of the sequence of elements the algorithm will be applied to.
f – Specifies the function (or function object) which will be invoked for each of the elements in the sequence specified by [first, last). The signature of this predicate should be equivalent to:
```
<ignored> pred(const Type &a);
```
The signature does not need to have const&. The type Type must be such that an object of type InIter can be dereferenced and then implicitly converted to Type.

Returns

template<typename ExPolicy, typename FwdIter, typename F> util::detail::algorithm_result<ExPolicy, void>::type for_each(ExPolicy &&policy, FwdIter first, FwdIter last, F &&f)#

Applies f to the result of dereferencing every iterator in the range [first, last). Executed according to the policy.

If f returns a result, the result is ignored.

If the type of first satisfies the requirements of a mutable iterator, f may apply non-constant functions through the dereferenced iterator.

Unlike its sequential form, the parallel overload of for_each does not return a copy of its Function parameter, since parallelization may not permit efficient state accumulation.

The application of function objects in parallel algorithm invoked with an execution policy object of type sequenced_policy execute in sequential order in the calling thread.

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: Applies f exactly last - first times.

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.
FwdIter – The type of the source begin and end iterator used (deduced). This iterator type must meet the requirements of a forward iterator.
F – The type of the function/function object to use (deduced). Unlike its sequential form, the parallel overload of for_each requires F to meet the requirements of CopyConstructible.

Parameters

policy – The execution policy to use for the scheduling of the iterations.
first – Refers to the beginning of the sequence of elements the algorithm will be applied to.
last – Refers to the end of the sequence of elements the algorithm will be applied to.
f – Specifies the function (or function object) which will be invoked for each of the elements in the sequence specified by [first, last). The signature of this predicate should be equivalent to:
```
<ignored> pred(const Type &a);
```
The signature does not need to have const&. The type Type must be such that an object of type FwdIter can be dereferenced and then implicitly converted to Type.

Returns

The for_each algorithm returns a hpx::future<void> if the execution policy is of type sequenced_task_policy or parallel_task_policy and returns void otherwise.

template<typename InIter, typename Size, typename F> InIter for_each_n(InIter first, Size count, F &&f)#

Applies f to the result of dereferencing every iterator in the range [first, first + count), starting from first and proceeding to first + count - 1.

If f returns a result, the result is ignored.

If the type of first satisfies the requirements of a mutable iterator, f may apply non-constant functions through the dereferenced iterator.

Note

Complexity: Applies f exactly count times.

Template Parameters

InIter – The type of the source begin and end iterator used (deduced). This iterator type must meet the requirements of an input iterator.
Size – The type of the argument specifying the number of elements to apply f to.
F – The type of the function/function object to use (deduced). F must meet requirements of MoveConstructible.

Parameters

first – Refers to the beginning of the sequence of elements the algorithm will be applied to.
count – Refers to the number of elements starting at first the algorithm will be applied to.
f – Specifies the function (or function object) which will be invoked for each of the elements in the sequence specified by [first, last). The signature of this predicate should be equivalent to:
```
<ignored> pred(const Type &a);
```
The signature does not need to have const&. The type Type must be such that an object of type InIter can be dereferenced and then implicitly converted to Type.

Returns

first + count for non-negative values of count and first for negative values.

template<typename ExPolicy, typename FwdIter, typename Size, typename F> util::detail::algorithm_result<ExPolicy, FwdIter>::type for_each_n(ExPolicy &&policy, FwdIter first, Size count, F &&f)#

Applies f to the result of dereferencing every iterator in the range [first, first + count), starting from first and proceeding to first + count - 1. Executed according to the policy.

If f returns a result, the result is ignored.

If the type of first satisfies the requirements of a mutable iterator, f may apply non-constant functions through the dereferenced iterator.

Unlike its sequential form, the parallel overload of for_each_n does not return a copy of its Function parameter, since parallelization may not permit efficient state accumulation.

The application of function objects in parallel algorithm invoked with an execution policy object of type sequenced_policy execute in sequential order in the calling thread.

Note

Complexity: Applies f exactly count times.

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.
FwdIter – The type of the source iterators used (deduced). This iterator type must meet the requirements of an forward iterator.
Size – The type of the argument specifying the number of elements to apply f to.
F – The type of the function/function object to use (deduced). Unlike its sequential form, the parallel overload of for_each_n requires F to meet the requirements of CopyConstructible.

Parameters

policy – The execution policy to use for the scheduling of the iterations.
first – Refers to the beginning of the sequence of elements the algorithm will be applied to.
count – Refers to the number of elements starting at first the algorithm will be applied to.
f – Specifies the function (or function object) which will be invoked for each of the elements in the sequence specified by [first, last). The signature of this predicate should be equivalent to:
```
<ignored> pred(const Type &a);
```
The signature does not need to have const&. The type Type must be such that an object of type FwdIter can be dereferenced and then implicitly converted to Type.

Returns

The for_each_n algorithm returns a hpx::future<FwdIter> if the execution policy is of type sequenced_task_policy or parallel_task_policy and returns FwdIter otherwise. It returns first + count for non-negative values of count and first for negative values.