std::transform_inclusive_scan

The generalized noncommutative sum of a sequence of elements over a binary 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 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:

• 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 undefined:

• For overloads (1,2), the value type of decltype(first) is not MoveConstructible.
• 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].

[edit] Parameters

[edit] Return value

Iterator to the element past the last element written.

[edit] Complexity

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

[edit] 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::terminate is called. For any other ExecutionPolicy, the behavior is implementation-defined.
• If the algorithm fails to allocate memory, std::bad_alloc is thrown.

[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';
}

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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