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std::transform_inclusive_scan

From cppreference.com
< cpp‎ | algorithm
 
 
Algorithm library
Execution policies (C++17)
Non-modifying sequence operations
(C++11)(C++11)(C++11)
(C++17)
Modifying sequence operations
Operations on uninitialized storage
Partitioning operations
Sorting operations
(C++11)
Binary search operations
Set operations (on sorted ranges)
Heap operations
(C++11)
Minimum/maximum operations
(C++11)
(C++17)

Permutations
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transform_inclusive_scan
(C++17)
C library
 
Defined in header <numeric>
template< class InputIt, class OutputIt,

          class UnaryOperation, class BinaryOperation >
OutputIt transform_inclusive_scan( InputIt first, InputIt last,
                                   OutputIt d_first, UnaryOperation unary_op,

                                   BinaryOperation binary_op );
(1) (since C++17)
template< class ExecutionPolicy, class InputIt, class OutputIt,

          class UnaryOperation, class BinaryOperation >
OutputIt transform_inclusive_scan( ExecutionPolicy&& policy,
                                   InputIt first, InputIt last,
                                   OutputIt d_first, UnaryOperation unary_op,

                                   BinaryOperation binary_op );
(2) (since C++17)
template< class InputIt, class OutputIt,

          class UnaryOperation, class BinaryOperation, class T >
OutputIt transform_inclusive_scan( InputIt first, InputIt last,
                                   OutputIt d_first, UnaryOperation unary_op,

                                   BinaryOperation binary_op, T init );
(3) (since C++17)
template< class ExecutionPolicy, class InputIt, class OutputIt,

          class UnaryOperation, class BinaryOperation, class T >
OutputIt transform_inclusive_scan( ExecutionPolicy&& policy,
                                   InputIt first, InputIt last,
                                   OutputIt d_first, UnaryOperation unary_op,

                                   BinaryOperation binary_op, T init );
(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 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, 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 or subranges, nor modify elements in the ranges [first, last) or [d_first, d_first + (last - first)). Otherwise, the behavior is undefined.

Contents

[edit] 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_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 InputIterator.
-
OutputIt must meet the requirements of OutputIterator.

[edit] Return value

Iterator to the element past the last element written.

[edit] Complexity

O(last - first) applications of each of binary_op and unary_op.

[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 three 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 not applied to init.

[edit] Example

[edit] See also

computes the partial sum of a range of elements
(function template) [edit]
applies a function to a range of elements
(function template) [edit]
similar to std::partial_sum, includes the ith input element in the ith sum
(function template) [edit]
applies a functor, then calculates exclusive scan
(function template) [edit]