std::transform_inclusive_scan
Defined in header <numeric>
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template< class InputIt, class OutputIt, class BinaryOperation, class UnaryOperation > |
(1) | (since C++17) |
template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2, class BinaryOperation, class UnaryOperation > |
(2) | (since C++17) |
template< class InputIt, class OutputIt, class BinaryOperation, class UnaryOperation, class T > |
(3) | (since C++17) |
template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2, class BinaryOperation, class UnaryOperation, class T > |
(4) | (since C++17) |
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 everyj
in [first, first + (i - d_first + 1)) overbinary_op
, - for overloads (3-4), the generalized noncommutative sum of
init, unary_op(*j)...
for everyj
in [first, first + (i - d_first + 1)) overbinary_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
, and do not participate in overload resolution unless std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> 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
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policy | - | the execution policy to use. See execution policy for details. |
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 .
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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.
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Type requirements | ||
-InputIt must meet the requirements of LegacyInputIterator.
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-OutputIt must meet the requirements of LegacyOutputIterator.
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-ForwardIt1 must meet the requirements of LegacyForwardIterator. and, if init is not provided, ForwardIt1's value_type must be MoveConstructible and binary_op(unary_op(*first), unary_op(*first)) must be convertible to ForwardIt1's value type
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-ForwardIt2 must meet the requirements of LegacyForwardIterator.
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-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
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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 otherExecutionPolicy
, 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
#include <functional> #include <iostream> #include <iterator> #include <numeric> #include <vector> int times_10(int x) { return x * 10; } int main() { std::vector data {3, 1, 4, 1, 5, 9, 2, 6}; 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
computes the partial sum of a range of elements (function template) | |
applies a function to a range of elements (function template) | |
(C++17) |
similar to std::partial_sum, includes the ith input element in the ith sum (function template) |
(C++17) |
applies a functor, then calculates exclusive scan (function template) |