Implement, document (i.e. provide specifications), and test the following function in Scheme. Scheme has implemented some of the constructs - you may not use these implementations, but rather must implement them yourself. Write a Scheme function (iterator (start step end)) which returns a function which when repeatedly called returns the numbers in the sequence (range (start step end)). When the sequence is exhausted the returned function should return (). Example: (define next (iterator '(0 2 7))), (begin (next) (next) (next) (next) (next)) => 0, 2, 4, 6, ()

The language used is Scheme