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Showing content from https://en.cppreference.com/w/cpp/language/../algorithm/../algorithm/transform_inclusive_scan.html below:

std::transform_inclusive_scan - cppreference.com

template< class InputIt, class OutputIt,

          class BinaryOp, class UnaryOp >
OutputIt transform_inclusive_scan
    ( InputIt first, InputIt last, OutputIt d_first,

      BinaryOp binary_op, UnaryOp unary_op );
(1) (since C++17)
(constexpr since C++20) template< class ExecutionPolicy,

          class ForwardIt1, class ForwardIt2,
          class BinaryOp, class UnaryOp >
ForwardIt2 transform_inclusive_scan
    ( ExecutionPolicy&& policy,
      ForwardIt1 first, ForwardIt1 last, ForwardIt2 d_first,

      BinaryOp binary_op, UnaryOp unary_op );
(2) (since C++17) template< class InputIt, class OutputIt,

          class BinaryOp, class UnaryOp, class T >
OutputIt transform_inclusive_scan
    ( InputIt first, InputIt last, OutputIt d_first,

      BinaryOp binary_op, UnaryOp unary_op, T init );
(3) (since C++17)
(constexpr since C++20) template< class ExecutionPolicy,

          class ForwardIt1, class ForwardIt2,
          class BinaryOp, class UnaryOp, class T >
ForwardIt2 transform_inclusive_scan
    ( ExecutionPolicy&& policy,
      ForwardIt1 first, ForwardIt1 last, ForwardIt2 d_first,

      BinaryOp binary_op, UnaryOp unary_op, T init );
(4) (since C++17)

1) Computes the inclusive prefix sum using op.

For each integer

i

in

[​0​std::distance(first, last))

, performs the following operations in order:

  1. Creates a sequence which is formed by the values transformed from the elements of [firstiter] in order by unary_op, where iter is the next ith iterator of first.
  2. Computes the generalized noncommutative sum of the sequence over binary_op.
  3. Assigns the result to *dest, where dest is the next ith iterator of d_first.

3) Same as (1), but each sequence created is formed by init followed by the elements of [firstiter] in order.

2,4) Same as (1,3), but executed according to policy.

These overloads participate in overload resolution only if all following conditions are satisfied:

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

  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 sequence.


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:

If any of the following conditions is satisfied, the behavior is undefined:

[edit] Parameters first, last - the pair of iterators defining 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 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 binary_op. binary_op - binary FunctionObject that will be applied in to the 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, ForwardIt2 must meet the requirements of LegacyForwardIterator. [edit] Return value

Iterator to the element past the last element written.

[edit] Complexity

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

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

[edit] Exceptions

The overloads with a template parameter named ExecutionPolicy report errors as follows:

[edit] Notes

unary_op is never applied to init.

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

[edit] Example
#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
[edit] See also

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