Defined in header
template<classInputIt,classOutputIt,classBinaryOp,classUnaryOp>OutputIttransform_inclusive_scan(InputItfirst,InputItlast,OutputItd_first,BinaryOpbinary_op,UnaryOpunary_op); (1) (since C++17)
(constexpr since C++20)template<classExecutionPolicy,classForwardIt1,classForwardIt2,classBinaryOp,classUnaryOp>ForwardIt2transform_inclusive_scan(ExecutionPolicy&&policy,ForwardIt1first,ForwardIt1last,ForwardIt2d_first,BinaryOpbinary_op,UnaryOpunary_op); (2) (since C++17)template<classInputIt,classOutputIt,classBinaryOp,classUnaryOp,classT>OutputIttransform_inclusive_scan(InputItfirst,InputItlast,OutputItd_first,BinaryOpbinary_op,UnaryOpunary_op,Tinit); (3) (since C++17)
(constexpr since C++20)template<classExecutionPolicy,classForwardIt1,classForwardIt2,classBinaryOp,classUnaryOp,classT>ForwardIt2transform_inclusive_scan(ExecutionPolicy&&policy,ForwardIt1first,ForwardIt1last,ForwardIt2d_first,BinaryOpbinary_op,UnaryOpunary_op,Tinit); (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:
Creates a sequence which is formed by the values transformed from the elements of [first, iter] in order by unary_op, where iter is the next ith iterator of first.
Computes the generalized noncommutative sum of the sequence over binary_op.
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 [first, iter] in order.
2,4) Same as (1,3), but executed according to policy.
These overloads participate in overload resolution only if the value of the following expression is true:
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)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:
Selects any two adjacent elements elem1 and elem2 from the sequence.
Calculates binary_op(elem1,elem2) and replaces the two elements in the sequence with the result.
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
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
.
For overloads (3,4), T is not
.
unary_op or binary_op modifies any element of [first, last).
unary_op or binary_op invalidates any iterator or subrange of [first, last].
Parameters
first, last - the pair of iterators defining the
of elements to sum d_first - the beginning of the destination range; may be equal to firstpolicy - the
to use init - the initial value unary_op - unary
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
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
. -OutputIt must meet the requirements of
. -ForwardIt1, ForwardIt2 must meet the requirements of
. Return value
Iterator to the element past the last element written.
Complexity
Given N as std::distance(first,last):
1-4)O(N) applications of unary_op and binary_op respectively.
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
,
is called. For any other ExecutionPolicy, the behavior is implementation-defined.
If the algorithm fails to allocate memory,
is thrown.
Notes
unary_op is never applied to init.
The parameter init appears last, differing from
, because it is optional for this function.
Example
Run this code
#include<functional>#include<iostream>#include<iterator>#include<numeric>#include<vector>intmain(){std::vectordata{3,1,4,1,5,9,2,6};autotimes_10=[](intx){returnx*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 See also