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 binary_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 arbitrary 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 execution policy
for details.
init - the initial value
unary FunctionObject that will be applied to each
unary_op - element of the input range. The return 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 MoveConstructible 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 MoveConstructible. 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::terminate 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_exclusive_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 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 ith input element
(C++17) in the ith sum
(function template)
transform_exclusive_scan applies an invocable, then calculates exclusive scan
(C++17) (function template)