std::for_each_n (3) - Linux Manuals
std::for_each_n - std::for_each_n
Defined in header <algorithm>
template< class InputIt, class Size, class UnaryFunction > (since C++17)
InputIt for_each_n( InputIt first, Size n, UnaryFunction f ); (until C++20)
template< class InputIt, class Size, class UnaryFunction > (1) (since C++20)
constexpr InputIt for_each_n( InputIt first, Size n, UnaryFunction f );
template< class ExecutionPolicy, class ForwardIt, class Size, class UnaryFunction2 > (2) (since C++17)
ForwardIt for_each_n( ExecutionPolicy&& policy, ForwardIt first, Size n, UnaryFunction2 f );
1) Applies the given function object f to the result of dereferencing every iterator in the range [first, first + n), in order.
2) Applies the given function object f to the result of dereferencing every iterator in the range [first, first + n) (not necessarily in order). The algorithm is executed according to policy. This overload does not participate in overload resolution unless std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is true.
For both overloads, if the iterator type is mutable, f may modify the elements of the range through the dereferenced iterator. If f returns a result, the result is ignored. If n is less than zero, the behavior is undefined.
first - the beginning of the range to apply the function to
n - the number of elements to apply the function to
policy - the execution policy to use. See execution_policy for details.
f - void fun(const Type &a);
InputIt must meet the requirements of LegacyInputIterator.
ForwardIt must meet the requirements of LegacyForwardIterator.
UnaryFunction must meet the requirements of MoveConstructible. Does not have to be CopyConstructible
UnaryFunction2 must meet the requirements of CopyConstructible.
first + n
Exactly n applications of f
The overload with a template parameter named ExecutionPolicy reports errors as follows:
* If execution of a function invoked as part of the algorithm throws an exception and ExecutionPolicy is one of the standard_policies, std::terminate is called. For any other ExecutionPolicy, the behavior is implementation-defined.
* If the algorithm fails to allocate memory, std::bad_alloc is thrown.
// Run this code
transform (function template)
range-for_loop executes loop over range (since C++11)
for_each (function template)