Use lazy evaluation (delay and force) to implement iterator objects in Scheme. More specifically, let an iterator be either the null list or a pair consisting of an element and a promise which when forced will return an iterator. Give code for an uptoby function that returns an iterator, and a for-iter function that accepts as arguments a one-argument function and an iterator. These should allow you to evaluate such expressions as (for-iter (lambda (e) (display e) (newline)) (uptoby 10 50 3))

Note that unlike the standard Scheme for-each, for-iter should not require the existence of a list containing the elements over which to iterate; the intrinsic space required for (for-iter f (uptoby 1 n 1)) should be only O(1), rather than O(n).