Category: algorithms | Component type: function |
template <class InputIterator, class T> T accumulate(InputIterator first, InputIterator last, T init); template <class InputIterator, class T, class BinaryFunction> T accumulate(InputIterator first, InputIterator last, T init, BinaryFunction binary_op);
The function object binary_op is not required to be either commutative or associative: the order of all of accumulate's operations is specified. The result is first initialized to init. Then, for each iterator i in [first, last), in order from beginning to end, it is updated by result = result + *i (in the first version) or result = binary_op(result, *i) (in the second version).
int main() { int A[] = {1, 2, 3, 4, 5}; const int N = sizeof(A) / sizeof(int); cout << "The sum of all elements in A is " << accumulate(A, A + N, 0) << endl; cout << "The product of all elements in A is " << accumulate(A, A + N, 1, multiplies<int>()) << endl; }
[1] There are several reasons why it is important that accumulate starts with the value init. One of the most basic is that this allows accumulate to have a well-defined result even if [first, last) is an empty range: if it is empty, the return value is init. If you want to find the sum of all of the elements in [first, last), you can just pass 0 as init.