accumulate

     Generalized Numeric Operation

Accumulate all elements within a range into a single value.

Contents

• Synopsis
• Description
• Complexity
• Example
• Warnings

#include <numeric>

template <class InputIterator, class T>
T accumulate (InputIterator first,
              InputIterator last,
              T init);
template <class InputIterator,
          class T,
          class BinaryOperation>
T accumulate (InputIterator first,
              InputIterator last,
              T init,
              BinaryOperation binary_op);

accumulate applies a binary operation to init and each value in the range [first,last). The result of each operation is returned in init. This process aggregates the result of performing the operation on every element of the sequence into a single value.

Accumulation is done by initializing the accumulator acc with the initial value init and then modifying it with acc = acc + *i or acc = binary_op(acc, *i) for every iterator i in the range [first, last) in order. If the sequence is empty, accumulate returns init.

accumulate performs exactly last-first applications of the binary operation (operator+ by default).

//
// accum.cpp
//
 #include <numeric>   //for accumulate
 #include <vector>    //for vector
 #include <functional> //for times
 #include <iostream.h>
 int main()
 {
   //
   //Typedef for vector iterators
   //
   typedef vector<int>::iterator iterator;
   //
   //Initialize a vector using an array of ints
   //
   int d1[10] = {1,2,3,4,5,6,7,8,9,10};
   vector<int> v1(d1, d1+10);
   //
   //Accumulate sums and products
   //
   int sum = accumulate(v1.begin(), v1.end(), 0);
   int prod = accumulate(v1.begin(), v1.end(), 
               1, times<int>());
   //
   //Output the results
   //
   cout << "For the series: ";
   for(iterator i = v1.begin(); i != v1.end(); i++)
       cout << *i << " ";
   cout << " where N = 10." << endl;
   cout << "The sum = (N*N + N)/2 = " << sum << endl;
   cout << "The product = N! = " << prod << endl;
   return 0;
 }
Output :
For the series: 1 2 3 4 5 6 7 8 9 10  where N = 10.
The sum = (N*N + N)/2 = 55
The product = N! = 3628800

If your compiler does not support default template parameters then you need to always supply the Allocator template argument. For instance you'll have to write:

vector<int,allocator>

instead of:

vector<int>