cppreference.com > C++ Algorithms > accumulate accumulate Syntax:
      #include <algorithm>
      TYPE accumulate( iterator start, iterator end, TYPE val );
      TYPE accumulate( iterator start, iterator end, TYPE val, BinaryFunction f );
The accummulate() 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. accumulate() runs in linear time. Related topics: adjacent_difference count inner_product partial_sum