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

NAME
     std::transform_inclusive_scan - std::transform_inclusive_scan

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

		  class  BinaryOp,  class  UnaryOp  >			  (since
     C++17)
	OutputIt transform_inclusive_scan			 (1)  (constexpr
     since C++20)
	    ( InputIt first, InputIt last, OutputIt d_first,

	      BinaryOp binary_op, UnaryOp unary_op );
	template< class ExecutionPolicy,

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

	      BinaryOp binary_op, UnaryOp unary_op );
	template< class InputIt, class OutputIt,

		  class BinaryOp, class  UnaryOp,  class  T  >		  (since
     C++17)
	OutputIt  transform_inclusive_scan			  (3) (constexpr
     since C++20)
	    ( InputIt first, InputIt last, OutputIt d_first,

	      BinaryOp binary_op, UnaryOp unary_op, T init );
	template< class ExecutionPolicy,

		  class ForwardIt1, class ForwardIt2,
		  class BinaryOp, class UnaryOp, class T >
	ForwardIt2  transform_inclusive_scan			    (4)   (since
     C++17)
	    ( ExecutionPolicy&& policy,
	      ForwardIt1 first, ForwardIt1 last, ForwardIt2
	d_first,

	      BinaryOp binary_op, UnaryOp unary_op, T init );

	1) Computes the inclusive prefix sum using op.
	For each integer i in [0, std::distance(first, last)), performs the fol-
     lowing
	operations in order:
	 1.  Creates  a  sequence which is formed by the values transformed from
     the elements
	    of [first, iter] in order by unary_op, where iter is the next i
	    th iterator of first.
	 2. Computes the generalized noncommutative sum of the sequence over bi-
     nary_op.
	 3. Assigns the result to *dest, where dest is the next i
	    th iterator of d_first.
	3) Same as (1), but each sequence created is formed by init followed  by
     the elements
	of [first, iter] in order.
	2,4) Same as (1,3), but executed according to policy.
	These overloads participate in overload resolution only if

	std::is_execution_policy_v<std::decay_t<ExecutionPolicy>>    is    true.
     (until
										  C++20)
	std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>>      is
     true. (since
										  C++20)

	The  generalized noncommutative sum of a sequence of elements over a bi-
     nary operation
	binary_op is defined as follows:

	  * If the sequence only has one element, the sum is the  value  of  the
     element.
	  * Otherwise, performs the following operations in order:
	 1. Selects any two adjacent elements elem1 and elem2 from the sequence.
	 2.  Calculates binary_op(elem1, elem2) and replaces the two elements in
     the sequence
	    with the result.
	 3. Repeats steps 1 and 2 until there is only one  element  in	the  se-
     quence.

	The  result  is  non-deterministic  if	the binary_op is not associative
     (such as
	floating-point addition).

	For overloads (1,2), if binary_op(unary_op(*first), unary_op(*first)) is
     not
	convertible to the value type of decltype(first), the  program	is  ill-
     formed.

	For  overloads	(3,4), if any of the following values is not convertible
     to T, the
	program is ill-formed:

	  * binary_op(init, init)
	  * binary_op(init, unary_op(*first))
	  * binary_op(unary_op(*first), unary_op(*first))

	If any of the following conditions is satisfied, the behavior  is  unde-
     fined:

	  *  For overloads (1,2), the value type of decltype(first) is not Move-
     Constructible.
	  * For overloads (3,4), T is not MoveConstructible.
	  * unary_op or binary_op modifies any element of [first, last).
	  * unary_op or  binary_op  invalidates  any  iterator	or  subrange  of
     [first, last].

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 execution policy for  de-
     tails.
	init	    - the initial value
	unary_op     - unary FunctionObject that will be applied to each element
     of the input
		      range. The return type must be acceptable as input to  bi-
     nary_op.
	binary_op    -	binary FunctionObject that will be applied in to the re-
     sult of
		      unary_op, the results of other binary_op, and init if pro-
     vided

Type requirements
	-
	InputIt must meet the requirements of LegacyInputIterator.
	-
	OutputIt must meet the requirements of LegacyOutputIterator.
	-
	ForwardIt1, ForwardIt2 must meet the requirements of LegacyForwardItera-
     tor.

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

Complexity
	Given \(\scriptsize N\)N as std::distance(first, last):

	1-4) \(\scriptsize O(N)\)O(N) applications of unary_op and binary_op re-
     spectively.

Exceptions
	The overloads with a template parameter named ExecutionPolicy report er-
     rors 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-de-
     fined.
	  * If the algorithm fails to allocate memory, std::bad_alloc is thrown.

Notes
	unary_op is never applied to init.

	The  parameter	init  appears last, differing from std::transform_exclu-
     sive_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);
	  std::cout << '\n';
      }

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 elements
				 (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 i^th
     input
	(C++17) 		 element in the i^th sum
				 (function template)
	transform_exclusive_scan applies an invocable, then calculates exclusive
     scan
	(C++17) 		 (function template)

http://cppreference.com 	   2024.06.10	   std::transf...clusive_scan(3)
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