=====accumulate=====
Syntax:

<code>
#include <numeric>
TYPE accumulate( input_iterator start, input_iterator end, TYPE val );
TYPE accumulate( input_iterator start, input_iterator end, TYPE val, BinaryFunction f );
</code>

The ''accumulate'' function computes the sum of ''val'' and all of the elements in
the range [''start'',''end'').

If the binary function ''f'' if specified, it is used instead of the ''+ operator'' to
perform the summation.

The ''accumulate'' function runs in [[/complexity|linear time]].

For example, the following code uses ''accumulate'' to sum the integers in a [[stl/vector/|vector]]:

<code>
#include <iostream>
using std::cout;
#include <vector>
using std::vector;
#include <numeric>
using std::accumulate;

int main() {
  vector<int> v;
  const int START = 1, END = 10;
  for( int i = START; i <= END; ++i ) v.push_back(i);

  int sum = accumulate( v.begin(), v.end(), 0 );

  cout << "sum from " << START << " to " << END << " is " << sum << '\n';
}
</code>

The ''accumulate'' function can also be used on non-numerical types.  The following
example uses ''accumulate'' to concatenate all of the [[string/|strings]] in a 
[[stl/vector/|vector]] into a single string:

<code>
int main () {
    string str = "Hello World!";
    vector<string> vec(10,str);   // vec = ["Hello World!", "Hello World!", ...]
    string a = accumulate( vec.begin(), vec.end(), string("") );
    cout << a << endl;            // displays "Hello World!Hello World!Hello..."
}
</code>

Related Topics: [[adjacent_difference]], [[count]], [[inner_product]], [[partial_sum]]