std::accumulate

sum (1)	template <class InputIterator, class T> T accumulate (InputIterator first, InputIterator last, T init);
custom (2)	template <class InputIterator, class T, class BinaryOperation> T accumulate (InputIterator first, InputIterator last, T init, BinaryOperation binary_op);

sum (1)

template <class InputIterator, class T> T accumulate (InputIterator first, InputIterator last, T init);

custom (2)

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:

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 ++first; } 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 an element of type T as first argument and an element in the range as second, and which returns a value that can be assigned to type T.
This can either be a function pointer or a function object.
The operation shall not modify the elements passed as its arguments.

Return value

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

Example

// accumulate example #include <iostream> // std::cout #include <functional> // std::minus #include <numeric> // std::accumulate 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}; std::cout << "using default accumulate: "; std::cout << std::accumulate(numbers,numbers+3,init); std::cout << '\n'; std::cout << "using functional's minus: "; std::cout << std::accumulate (numbers, numbers+3, init, std::minus<int>()); std::cout << '\n'; std::cout << "using custom function: "; std::cout << std::accumulate (numbers, numbers+3, init, myfunction); std::cout << '\n'; std::cout << "using custom object: "; std::cout << std::accumulate (numbers, numbers+3, init, myobject); std::cout << '\n'; return 0; }

Output:

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

Complexity

Linear in the distance between first and last.

Data races

The elements in the range [first,last) are accessed (each element is accessed exactly once).

Exceptions

Throws if any of binary_op, the assignments or an operation on an iterator throws.
Note that invalid arguments cause undefined behavior.