Exercise 4.35: Write a procedure
an-integer-between that returns an integer between two given bounds.
This can be used to implement a procedure that finds Pythagorean triples, i.e.,
triples of integers 
  
    (
    i
    ,
    j
    ,
    k
    )
  
 between the given bounds such that

  
    i
    ≤
    j
  
 and 
  
    
      i
      2
    
    +
    
      j
      2
    
    =
    
      k
      2
    
  
, as follows:


(define (a-pythagorean-triple-between low high)
  (let ((i (an-integer-between low high)))
    (let ((j (an-integer-between i high)))
      (let ((k (an-integer-between j high)))
        (require (= (+ (* i i) (* j j)) 
                    (* k k)))
        (list i j k)))))