# 28 Algorithms library [algorithms]

## 28.5 Non-modifying sequence operations [alg.nonmodifying]

### 28.5.4 For each [alg.foreach]

```template<class InputIterator, class Function> Function for_each(InputIterator first, InputIterator last, Function f); ```

Requires: Function shall meet the requirements of MoveConstructible. [Note: Function need not meet the requirements of CopyConstructible. end note]

Effects: Applies f to the result of dereferencing every iterator in the range [first, last), starting from first and proceeding to last - 1. [Note: If the type of first satisfies the requirements of a mutable iterator, f may apply non-constant functions through the dereferenced iterator.end note]

Returns: f.

Complexity: Applies f exactly last - first times.

Remarks: If f returns a result, the result is ignored.

```template<class ExecutionPolicy, class ForwardIterator, class Function> void for_each(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last, Function f); ```

Requires: Function shall meet the requirements of CopyConstructible.

Effects: Applies f to the result of dereferencing every iterator in the range [first, last). [Note: If the type of first satisfies the requirements of a mutable iterator, f may apply non-constant functions through the dereferenced iterator. end note]

Complexity: Applies f exactly last - first times.

Remarks: If f returns a result, the result is ignored. Implementations do not have the freedom granted under [algorithms.parallel.exec] to make arbitrary copies of elements from the input sequence.

[Note: Does not return a copy of its Function parameter, since parallelization may not permit efficient state accumulation. end note]

```template<class InputIterator, class Size, class Function> InputIterator for_each_n(InputIterator first, Size n, Function f); ```

Requires: Function shall meet the requirements of MoveConstructible [Note: Function need not meet the requirements of CopyConstructible. end note]

Requires: n >= 0.

Effects: Applies f to the result of dereferencing every iterator in the range [first, first + n) in order. [Note: If the type of first satisfies the requirements of a mutable iterator, f may apply non-constant functions through the dereferenced iterator. end note]

Returns: first + n.

Remarks: If f returns a result, the result is ignored.

```template<class ExecutionPolicy, class ForwardIterator, class Size, class Function> ForwardIterator for_each_n(ExecutionPolicy&& exec, ForwardIterator first, Size n, Function f); ```

Requires: Function shall meet the requirements of CopyConstructible.

Requires: n >= 0.

Effects: Applies f to the result of dereferencing every iterator in the range [first, first + n). [Note: If the type of first satisfies the requirements of a mutable iterator, f may apply non-constant functions through the dereferenced iterator. end note]

Returns: first + n.

Remarks: If f returns a result, the result is ignored. Implementations do not have the freedom granted under [algorithms.parallel.exec] to make arbitrary copies of elements from the input sequence.