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std::transf...clusive_scan(3) C++ Standard Libarystd::transf...clusive_scan(3)

NAME
       std::transform_inclusive_scan - std::transform_inclusive_scan

Synopsis
	  Defined in header <numeric>
	  template< class InputIt, class OutputIt,

	  class	BinaryOperation, class UnaryOperation >
	  OutputIt   transform_inclusive_scan(	 InputIt		(since
       C++17)
	  first,  InputIt  last,  OutputIt  d_first,			(until
       C++20)

	  BinaryOperation binary_op, UnaryOperation
	  unary_op );
	  template< class InputIt, class OutputIt,

	  class	BinaryOperation, class UnaryOperation >
	  constexpr OutputIt transform_inclusive_scan(
	  InputIt   first,  InputIt  last,				(since
       C++20)
	  OutputIt d_first,
	  BinaryOperation binary_op,

	  UnaryOperation unary_op );
	  template< class ExecutionPolicy, class
	  ForwardIt1, class ForwardIt2,

	  class	BinaryOperation, class UnaryOperation >
	  ForwardIt2 transform_inclusive_scan(
	  ExecutionPolicy&&  policy,				  (2)	(since
       C++17)
	  ForwardIt1 first, ForwardIt1 last, ForwardIt2
	  d_first,

	  BinaryOperation binary_op, UnaryOperation
	  unary_op );
	  template< class InputIt, class OutputIt,

	  class	BinaryOperation, class UnaryOperation,	   (1)
	  class	T >
	  OutputIt		transform_inclusive_scan(	       InputIt
       (since C++17)
	  first,	InputIt	       last,	     OutputIt	      d_first,
       (until C++20)
	  BinaryOperation binary_op, UnaryOperation
	  unary_op,

	  T init );
	  template< class InputIt, class OutputIt,

	  class	BinaryOperation, class UnaryOperation,
	  class	T >
	  constexpr OutputIt transform_inclusive_scan(
	  InputIt		first,		    InputIt		 last,
       (since C++20)
	  OutputIt d_first,				       (3)
	  BinaryOperation binary_op,
	  UnaryOperation unary_op,

	  T init );
	  template< class ExecutionPolicy, class
	  ForwardIt1, class ForwardIt2,

	  class	BinaryOperation, class UnaryOperation,
	  class	T >
	  ForwardIt2 transform_inclusive_scan(
	  ExecutionPolicy&&	policy,					   (4)
       (since C++17)
	  ForwardIt1 first, ForwardIt1 last, ForwardIt2
	  d_first,
	  BinaryOperation binary_op, UnaryOperation
	  unary_op,

	  T init );

	  Transforms  each  element  in	the range [first, last)	with unary_op,
       then computes an
	  inclusive prefix sum operation using binary_op  over	the  resulting
       range, optionally
	  with	init as	the initial value, and writes the results to the range
       beginning at
	  d_first. "inclusive" means that the i-th input element  is  included
       in the i-th sum.

	  Formally,  assigns  through  each  iterator i	in [d_first, d_first +
       (last - first)) the
	  value	of

	    * for overloads  (1-2),  the  generalized  noncommutative  sum  of
       unary_op(*j)... for
	      every j in [first, first + (i - d_first +	1)) over binary_op,
	    * for overloads (3-4), the generalized noncommutative sum of init,
       unary_op(*j)...
	      for  every  j  in	 [first,  first	 + (i -	d_first	+ 1)) over bi-
       nary_op,

	  where	generalized noncommutative sum GNSUM(op, a
	  1, ..., a
	  N) is	defined	as follows:

	    * if N=1, a
	      1
	    * if N > 1,	op(GNSUM(op, a
	      1, ..., a
	      K), GNSUM(op, a
	      M, ..., a
	      N)) for any K where 1 < K+1 = M  N

	  In other words, the summation	operations may be performed  in	 arbi-
       trary order, and
	  the behavior is nondeterministic if binary_op	is not associative.

	  Overloads  (2,  4) are executed according to policy. These overloads
       do not
	  participate in overload resolution unless
	  std::is_execution_policy_v<std::decay_t<ExecutionPolicy>>
	  (until C++20)
	  std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>>
	  (since C++20)	is true.

	  unary_op and binary_op shall not invalidate iterators	(including the
       end iterators)
	  or subranges,	nor modify elements in the  ranges  [first,  last)  or
       [d_first, d_first +
	  (last	- first)). Otherwise, the behavior is undefined.

Parameters
	  first, last		-	  the range of elements	to sum
	  d_first		 -	    the	 beginning  of the destination
       range; may be equal
					  to first
	  policy		-	  the execution	policy to use. See ex-
       ecution policy
					  for details.
	  init			-	  the initial value
					  unary	FunctionObject	that  will  be
       applied to each
	  unary_op		 -	   element of the input	range. The re-
       turn type must be
					  acceptable as	input to binary_op.
					  binary FunctionObject	that  will  be
       applied in to the
	  binary_op		 -	    result of unary_op,	the results of
       other binary_op,
					  and init if provided.

Type requirements
	  -
	  InputIt must meet the	requirements of	LegacyInputIterator.
	  -
	  OutputIt must	meet the requirements of LegacyOutputIterator.
	  -
	  ForwardIt1 must meet the requirements	of LegacyForwardIterator.
	  -
	  ForwardIt2 must meet the requirements	of LegacyForwardIterator.
	  -
	  If init is not provided, decltype(first)'s value type	must be	 Move-
       Constructible and
	  binary_op(unary_op(*first), unary_op(*first))	must be	convertible to
	  decltype(first)'s value type
	  -
	  T  (if  init	is  provided)  must  meet the requirements of MoveCon-
       structible. All of
	  binary_op(init, unary_op(*first)), binary_op(init, init), and
	  binary_op(unary_op(*first), unary_op(*first))	must be	convertible to
       T

Return value
	  Iterator to the element past the last	element	written.

Complexity
	  O(last - first) applications of each of binary_op and	unary_op.

Exceptions
	  The overloads	with a template	parameter named	ExecutionPolicy	report
       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::termi-
       nate is called.
	      For  any	other ExecutionPolicy, the behavior is implementation-
       defined.
	    * If the algorithm fails to	 allocate  memory,  std::bad_alloc  is
       thrown.

Notes
	  unary_op is not applied to init.

	  The  parameter  init appears last, differing from std::transform_ex-
       clusive_scan,
	  because it is	optional for this function.

Example
       // Run this code

	#include <functional>
	#include <iostream>
	#include <iterator>
	#include <numeric>
	#include <vector>

	int main()
	{
	  std::vector data {3, 1, 4, 1,	5, 9, 2, 6};

	  auto times_10	= [](int x) { return x * 10; };

	  std::cout << "10 times exclusive sum:	";
	  std::transform_exclusive_scan(data.begin(), data.end(),
					std::ostream_iterator<int>(std::cout,
       " "),
					0, std::plus<int>{}, times_10);
	  std::cout << "\n10 times inclusive sum: ";
	  std::transform_inclusive_scan(data.begin(), data.end(),
					std::ostream_iterator<int>(std::cout,
       " "),
					std::plus<int>{}, times_10);
	}

Output:
	10 times exclusive sum:	0 30 40	80 90 140 230 250
	10 times inclusive sum:	30 40 80 90 140	230 250	310

See also
	  partial_sum		   computes the	partial	sum of a range of ele-
       ments
				   (function template)
				   applies a function to a range of  elements,
       storing results
	  transform		   in a	destination range
				   (function template)
	  inclusive_scan	    similar  to	std::partial_sum, includes the
       ith input element
	  (C++17)		   in the ith sum
				   (function template)
	  transform_exclusive_scan applies an invocable, then  calculates  ex-
       clusive scan
	  (C++17)		   (function template)

http://cppreference.com		  2022.07.31	 std::transf...clusive_scan(3)

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