Exercise 3.63: Louis Reasoner asks why the
sqrt-stream procedure was not written in the following more
straightforward way, without the local variable guesses:


(define (sqrt-stream x)
  (cons-stream 
   1.0
   (stream-map (lambda (guess)
                 (sqrt-improve guess x))
               (sqrt-stream x))))

Alyssa P. Hacker replies that this version of the procedure is considerably
less efficient because it performs redundant computation.  Explain Alyssa’s
answer.  Would the two versions still differ in efficiency if our
implementation of delay used only (lambda () ⟨exp⟩) without
using the optimization provided by memo-proc (3.5.1)?