<numeric> functions
The latest version of this topic can be found at <numeric> functions.
| accumulate | adjacent_difference | inner_product |
| iota | partial_sum |
accumulate
Computes the sum of all the elements in a specified range including some initial value by computing successive partial sums or computes the result of successive partial results similarly obtained from using a specified binary operation other than the sum.
template <class InputIterator, class Type>
Type accumulate(InputIterator first, InputIterator last, Type val);
template <class InputIterator, class Type, class BinaryOperation>
Type accumulate(InputIterator first, InputIterator last, Type val, BinaryOperation _Binary_op);
Parameters
first
An input iterator addressing the first element in the range to be summed or combined according to a specified binary operation.
last
An input iterator addressing the last element in the range to be summed or combined according to a specified binary operation that is one position beyond the final element actually included in the iterated accumulation.
val
An initial value to which each element is in turn added or combined with according to a specified binary operation.
_Binary_op
The binary operation that is to be applied to the each element in the specified range and the result of its previous applications.
Return Value
The sum of val and all the elements in the specified range for the first template function, or, for the second template function, the result of applying the binary operation specified, instead of the sum operation, to ( PartialResult, *Iter), where PartialResult is the result of previous applications of the operation and Iter is an iterator pointing to an element in the range.
Remarks
The initial value insures that there will be a well-defined result when the range is empty, in which case val is returned. The binary operation does not need to be associative or commutative. The result is initialized to the initial value val and then result = _Binary_op ( result, *Iter) is calculated iteratively through the range, where Iter is an iterator pointing to successive element in the range. The range must be valid and the complexity is linear with the size of the range. The return type of the binary operator must be convertible to Type to ensure closure during the iteration.
Example
// numeric_accum.cpp
// compile with: /EHsc
#include <vector>
#include <numeric>
#include <functional>
#include <iostream>
int main( )
{
using namespace std;
vector <int> v1, v2(20);
vector <int>::iterator iter1, iter2;
int i;
for (i = 1; i < 21; i++)
{
v1.push_back(i);
}
cout << "The original vector v1 is:\n ( " ;
for (iter1 = v1.begin(); iter1 != v1.end(); iter1++)
cout << *iter1 << " ";
cout << ")." << endl;
// The first member function for the accumulated sum
int total;
total = accumulate(v1.begin(), v1.end(), 0);
cout << "The sum of the integers from 1 to 20 is: "
<< total << "." << endl;
// Constructing a vector of partial sums
int j = 0, partotal;
for (iter1 = v1.begin(); iter1 != v1.end(); iter1++)
{
partotal = accumulate(v1.begin(), iter1 + 1, 0);
v2[j] = partotal;
j++;
}
cout << "The vector of partial sums is:\n ( " ;
for (iter2 = v2.begin(); iter2 != v2.end(); iter2++)
cout << *iter2 << " ";
cout << ")." << endl << endl;
// The second member function for the accumulated product
vector <int> v3, v4(10);
vector <int>::iterator iter3, iter4;
int s;
for (s = 1; s < 11; s++)
{
v3.push_back(s);
}
cout << "The original vector v3 is:\n ( " ;
for (iter3 = v3.begin(); iter3 != v3.end(); iter3++)
cout << *iter3 << " ";
cout << ")." << endl;
int ptotal;
ptotal = accumulate(v3.begin(), v3.end(), 1, multiplies<int>());
cout << "The product of the integers from 1 to 10 is: "
<< ptotal << "." << endl;
// Constructing a vector of partial products
int k = 0, ppartotal;
for (iter3 = v3.begin(); iter3 != v3.end(); iter3++) {
ppartotal = accumulate(v3.begin(), iter3 + 1, 1, multiplies<int>());
v4[k] = ppartotal;
k++;
}
cout << "The vector of partial products is:\n ( " ;
for (iter4 = v4.begin(); iter4 != v4.end(); iter4++)
cout << *iter4 << " ";
cout << ")." << endl;
}
The original vector v1 is:
( 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 ).
The sum of the integers from 1 to 20 is: 210.
The vector of partial sums is:
( 1 3 6 10 15 21 28 36 45 55 66 78 91 105 120 136 153 171 190 210 ).
The original vector v3 is:
( 1 2 3 4 5 6 7 8 9 10 ).
The product of the integers from 1 to 10 is: 3628800.
The vector of partial products is:
( 1 2 6 24 120 720 5040 40320 362880 3628800 ).
adjacent_difference
Computes the successive differences between each element and its predecessor in an input range and outputs the results to a destination range or computes the result of a generalized procedure where the difference operation is replaced by another, specified binary operation.
template <class InputIterator, class OutIterator>
OutputIterator adjacent_difference(InputIterator first, InputIterator last, OutputIterator _Result);
template <class InputIterator, class OutIterator, class BinaryOperation>
OutputIterator adjacent_difference(InputIterator first, InputIterator last, OutputIterator _Result, BinaryOperation _Binary_op);
Parameters
first
An input iterator addressing the first element in the input range whose elements are to be differenced with their respective predecessors or where the pair of values is to be operated on by another specified binary operation.
last
An input iterator addressing the last element in the input range whose elements are to be differenced with their respective predecessors or where the pair of values is to be operated on by another specified binary operation.
_Result
An output iterator addressing the first element a destination range where the series of differences or the results of the specified operation is to be stored.
_Binary_op
The binary operation that is to be applied in the generalized operation replacing the operation of subtraction in the differencing procedure.
Return Value
An output iterator addressing the end of the destination range: _Result + ( last - first).
Remarks
The output iterator _ Result is allowed to be the same iterator as the input iterator * first,* so that adjacent_differences may be computed in place.
For a sequence of values a1, a2, a3, in an input range, the first template function stores successive partial_differences a1, a2 - a1, a3 – a2, in the destination range.
For a sequence of values a1, a2, a3, in an input range, the second template function stores successive partial_differences a1, a2 _Binary_op a1, a3 _Binary_op a2, in the destination range.
The binary operation _Binary_op is not required to be either associative or commutative, because the order of operations applies is completely specified.
Example
// numeric_adj_diff.cpp
// compile with: /EHsc
#include <vector>
#include <list>
#include <numeric>
#include <functional>
#include <iostream>
int main( )
{
using namespace std;
vector<int> V1( 10 ), V2( 10 );
vector<int>::iterator VIter1, VIter2, VIterend, VIterend2;
list <int> L1;
list <int>::iterator LIter1, LIterend, LIterend2;
int t;
for ( t = 1 ; t <= 10 ; t++ )
{
L1.push_back( t * t );
}
cout << "The input list L1 is:\n ( " ;
for ( LIter1 = L1.begin( ) ; LIter1 != L1.end( ) ; LIter1++ )
cout << *LIter1 << " ";
cout << ")." << endl;
// The first member function for the adjacent_differences of
// elements in a list output to a vector
VIterend = adjacent_difference ( L1.begin ( ) , L1.end ( ) ,
V1.begin ( ) );
cout << "Output vector containing adjacent_differences is:\n ( " ;
for ( VIter1 = V1.begin( ) ; VIter1 != VIterend ; VIter1++ )
cout << *VIter1 << " ";
cout << ")." << endl;
// The second member function used to compute
// the adjacent products of the elements in a list
VIterend2 = adjacent_difference ( L1.begin ( ) , L1.end ( ) , V2.begin ( ) ,
multiplies<int>( ) );
cout << "The output vector with the adjacent products is:\n ( " ;
for ( VIter2 = V2.begin( ) ; VIter2 != VIterend2 ; VIter2++ )
cout << *VIter2 << " ";
cout << ")." << endl;
// Computation of adjacent_differences in place
LIterend2 = adjacent_difference ( L1.begin ( ) , L1.end ( ) , L1.begin ( ) );
cout << "In place output adjacent_differences in list L1 is:\n ( " ;
for ( LIter1 = L1.begin( ) ; LIter1 != LIterend2 ; LIter1++ )
cout << *LIter1 << " ";
cout << ")." << endl;
}
inner_product
Computes the sum of the element-wise product of two ranges and adds it to a specified initial value or computes the result of a generalized procedure where the sum and product binary operations are replaced by other specified binary operations.
template <class InputIterator1, class InputIterator2, class Type>
Type inner_product(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, Type val);
template <class InputIterator1, class InputIterator2, class Type, class BinaryOperation1, class BinaryOperation2>
Type inner_product(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, Type val, BinaryOperation1 _Binary_op1, BinaryOperation2 _Binary_op2);
Parameters
first1
An input iterator addressing the first element in the first range whose inner product or generalized inner product with the second range is to be computed.
last1
An input iterator addressing the last element in the first range whose inner product or generalized inner product with the second range is to be computed.
first2
An input iterator addressing the first element in the second range whose inner product or generalized inner product with the first range is to be computed.
val
An initial value to which the inner product or generalized inner product between the ranges is to be added.
_Binary_op1
The binary operation that replaces the inner product operation of sum applied to the element-wise products in the generalization of the inner product.
_Binary_op2
The binary operation that replaces the inner product element-wise operation of multiply in the generalization of the inner product.
Return Value
The first member function returns the sum of the element-wise products and adds to it the specified initial value. So for ranges of values ai and bi, it returns:
val + ( a1 * b1 ) + ( a2 * b2 ) +
by iteratively replacing val with val + (* ai * * bi ).
The second member function returns:
val _ Binary_op1 ( a1 _ Binary_op2 b1 ) _ Binary_op1 ( a2 _ Binary_op2 b2 ) _ Binary_op1
by iteratively replacing val with val _ Binary_op1 (* ai _ Binary_op2 * bi ).
Remarks
The initial value ensures that there will be a well-defined result when the range is empty, in which case val is returned. The binary operations do not need to be associative or commutative. The range must be valid and the complexity is linear with the size of the range. The return type of the binary operator must be convertible to Type to ensure closure during the iteration.
Example
// numeric_inner_prod.cpp
// compile with: /EHsc
#include <vector>
#include <list>
#include <numeric>
#include <functional>
#include <iostream>
int main()
{
using namespace std;
vector <int> v1, v2(7), v3(7);
vector <int>::iterator iter1, iter2, iter3;
int i;
for (i = 1; i <= 7; i++)
{
v1.push_back(i);
}
cout << "The original vector v1 is:\n ( " ;
for (iter1 = v1.begin(); iter1 != v1.end(); iter1++)
cout << *iter1 << " ";
cout << ")." << endl;
list <int> l1, l2(7);
list <int>::iterator lIter1, lIter2;
int t;
for (t = 1; t <= 7; t++)
{
l1.push_back(t);
}
cout << "The original list l1 is:\n ( " ;
for (lIter1 = l1.begin(); lIter1 != l1.end(); lIter1++)
cout << *lIter1 << " ";
cout << ")." << endl;
// The first member function for the inner product
int inprod;
inprod = inner_product(v1.begin(), v1.end(), l1.begin(), 0);
cout << "The inner_product of the vector v1 and the list l1 is: "
<< inprod << "." << endl;
// Constructing a vector of partial inner_products between v1 & l1
int j = 0, parinprod;
for (iter1 = v1.begin(); iter1 != v1.end(); iter1++) {
parinprod = inner_product(v1.begin(), iter1 + 1, l1.begin(), 0);
v2[j] = parinprod;
j++;
}
cout << "Vector of partial inner_products between v1 & l1 is:\n ( " ;
for (iter2 = v2.begin(); iter2 != v2.end(); iter2++)
cout << *iter2 << " ";
cout << ")." << endl << endl;
// The second member function used to compute
// the product of the element-wise sums
int inprod2;
inprod2 = inner_product (v1.begin(), v1.end(),
l1.begin(), 1, multiplies<int>(), plus<int>());
cout << "The sum of the element-wise products of v1 and l1 is: "
<< inprod2 << "." << endl;
// Constructing a vector of partial sums of element-wise products
int k = 0, parinprod2;
for (iter1 = v1.begin(); iter1 != v1.end(); iter1++)
{
parinprod2 =
inner_product(v1.begin(), iter1 + 1, l1.begin(), 1,
multiplies<int>(), plus<int>());
v3[k] = parinprod2;
k++;
}
cout << "Vector of partial sums of element-wise products is:\n ( " ;
for (iter3 = v3.begin(); iter3 != v3.end(); iter3++)
cout << *iter3 << " ";
cout << ")." << endl << endl;
}
iota
Stores a starting value, beginning with the first element and filling with successive increments of that value ( value++) in each of the elements in the interval [ first, last).
template <class ForwardIterator, class Type>
void iota(ForwardIterator first, ForwardIterator last, Type value);
Parameters
first
An input iterator that addresses the first element in the range to be filled.
last
An input iterator that addresses the last element in the range to be filled.
value
The starting value to store in the first element and to successively increment for subsequent elements.
Remarks
Example
The following example demonstrates some uses for the iota function by filling a list of integers and then filling a vector with the list so that the random_shuffle function can be used.
// compile by using: cl /EHsc /nologo /W4 /MTd
#include <algorithm>
#include <numeric>
#include <list>
#include <vector>
#include <iostream>
using namespace std;
int main(void)
{
list <int> intList(10);
vector <list<int>::iterator> intVec(intList.size());
// Fill the list
iota(intList.begin(), intList.end(), 0);
// Fill the vector with the list so we can shuffle it
iota(intVec.begin(), intVec.end(), intList.begin());
random_shuffle(intVec.begin(), intVec.end());
// Output results
cout << "Contents of the integer list: " << endl;
for (auto i: intList) {
cout << i << ' ';
}
cout << endl << endl;
cout << "Contents of the integer list, shuffled by using a vector: " << endl;
for (auto i: intVec) {
cout << *i << ' ';
}
cout << endl;
}
partial_sum
Computes a series of sums in an input range from the first element through the ith element and stores the result of each such sum in the ith element of a destination range or computes the result of a generalized procedure where the sum operation is replaced by another specified binary operation.
template <class InputIterator, class OutIt>
OutputIterator partial_sum(InputIterator first, InputIterator last, OutputIterator _Result);
template <class InputIterator, class OutIt, class Fn2>
OutputIterator partial_sum(InputIterator first, InputIterator last, OutputIterator _Result, BinaryOperation _Binary_op);
Parameters
first
An input iterator addressing the first element in the range to be partially summed or combined according to a specified binary operation.
last
An input iterator addressing the last element in the range to be partially summed or combined according to a specified binary operation that is one position beyond the final element actually included in the iterated accumulation.
_Result
An output iterator addressing the first element a destination range where the series of partial sums or the results of the specified operation is to be stored.
_Binary_op
The binary operation that is to be applied in the generalized operation replacing the operation of sum in the partial sum procedure.
Return Value
An output iterator addressing the end of the destination range: _Result + ( last - first),
Remarks
The output iterator _Result is allowed to be the same iterator as the input iterator first, so that partial sums may be computed in place.
For a sequence of values a1, a2, a3, in an input range, the first template function stores successive partial sums in the destination range, where the ith element is given by ( ( ( a1 + a2) + a3) ai).
For a sequence of values a1, a2, a3, in an input range, the second template function stores successive partial sums in the destination range, where the ith element is given by ( ( ( a1_Binary_op a2 ) _Binary_op a3 ) ai).
The binary operation _Binary_op is not required to be either associative or commutative, because the order of operations applies is completely specified.
Example
// numeric_partial_sum.cpp
// compile with: /EHsc
#include <vector>
#include <list>
#include <numeric>
#include <functional>
#include <iostream>
int main( )
{
using namespace std;
vector<int> V1( 10 ), V2( 10 );
vector<int>::iterator VIter1, VIter2, VIterend, VIterend2;
list <int> L1;
list <int>::iterator LIter1, LIterend;
int t;
for ( t = 1 ; t <= 10 ; t++ )
{
L1.push_back( t );
}
cout << "The input list L1 is:\n ( " ;
for ( LIter1 = L1.begin( ) ; LIter1 != L1.end( ) ; LIter1++ )
cout << *LIter1 << " ";
cout << ")." << endl;
// The first member function for the partial sums of
// elements in a list output to a vector
VIterend = partial_sum ( L1.begin ( ) , L1.end ( ) ,
V1.begin ( ) );
cout << "The output vector containing the partial sums is:\n ( " ;
for ( VIter1 = V1.begin( ) ; VIter1 != VIterend ; VIter1++ )
cout << *VIter1 << " ";
cout << ")." << endl;
// The second member function used to compute
// the partial product of the elements in a list
VIterend2 = partial_sum ( L1.begin ( ) , L1.end ( ) , V2.begin ( ) ,
multiplies<int>( ) );
cout << "The output vector with the partial products is:\n ( " ;
for ( VIter2 = V2.begin( ) ; VIter2 != VIterend2 ; VIter2++ )
cout << *VIter2 << " ";
cout << ")." << endl;
// Computation of partial sums in place
LIterend = partial_sum ( L1.begin ( ) , L1.end ( ) , L1.begin ( ) );
cout << "The in place output partial_sum list L1 is:\n ( " ;
for ( LIter1 = L1.begin( ) ; LIter1 != LIterend ; LIter1++ )
cout << *LIter1 << " ";
cout << ")." << endl;
}