accumulate


function template
<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 values in range

Returns the result of accumulating all the values in the range [first,last) to init.

The default operation is to add the elements up, but a different operation can be specified as binary_op.

The behavior of this function template is equivalent to:
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template <class InputIterator, class T>
   T accumulate ( InputIterator first, InputIterator last, T init )
{
  while ( first!=last )
    init = init + *first++;  // or: init=binary_op(init,*first++) for the binary_op version
  return init;
}


Parameters

first, last
Input iterators to the initial and final positions in a sequence. The range used is [first,last), which contains all the elements between first and last, including the element pointed by first but not the element pointed by last.
init
Initial value for the accumulator.
binary_op
Binary operation taking two elements of type T as argument, and returning the result of an accumulation operation. This can either be a pointer to a function or an object whose class overloads operator().


Return value

The result of accumulating init and all the elements in the range [first,last).

Example

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// accumulate example
#include <iostream>
#include <functional>
#include <numeric>
using namespace std;

int myfunction (int x, int y) {return x+2*y;}
struct myclass {
	int operator()(int x, int y) {return x+3*y;}
} myobject;

int main () {
  int init = 100;
  int numbers[] = {10,20,30};

  cout << "using default accumulate: ";
  cout << accumulate(numbers,numbers+3,init);
  cout << endl;

  cout << "using functional's minus: ";
  cout << accumulate (numbers, numbers+3, init, minus<int>() );
  cout << endl;

  cout << "using custom function: ";
  cout << accumulate (numbers, numbers+3, init, myfunction );
  cout << endl;

  cout << "using custom object: ";
  cout << accumulate (numbers, numbers+3, init, myobject );
  cout << endl;

  return 0;
}


Output:

using default accumulate: 160
using functional's minus: 40
using custom function: 220
using custom object: 280


See also

inner_product Compute cumulative inner product of range (function template)
partial_sum Compute partial sums of range (function template)
adjacent_difference Compute adjacent difference of range (function template)