sum function in cpp code example

Example: sum array c++

//Syntax
accumulate(first, last, sum);
accumulate(first, last, sum, myfun); 

first, last : first and last elements of range 
              whose elements are to be added
sum :  initial value of the sum
myfun : a function for performing any 
        specific task. For example, we can
        find product of elements between
        first and last.
//Example
  int a[] = {5 , 10 , 15} ;
  int res = accumulate(a,a+3,0); // 30