26 Numerics library [numerics]

26.7 Generalized numeric operations [numeric.ops]

26.7.2 Accumulate [accumulate]

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

Effects: Computes its result by initializing the accumulator acc with the initial value init and then modifies it with acc = acc + *i or acc = binary_op(acc, *i) for every iterator i in the range [first,last) in order.289

Requires: T shall meet the requirements of CopyConstructible (Table [copyconstructible]) and CopyAssignable (Table [copyassignable]) types. In the range [first,last], binary_op shall neither modify elements nor invalidate iterators or subranges.290

accumulate is similar to the APL reduction operator and Common Lisp reduce function, but it avoids the difficulty of defining the result of reduction on an empty sequence by always requiring an initial value.

The use of fully closed ranges is intentional