3.7.2.1 Examples of Transfer of Control during a Destructive Operation

The following examples illustrate some of the many ways in which the implementation-dependent nature of the modification can manifest itself.

      (let ((a (list 2 1 4 3 7 6 'five)))
        (ignore-errors (sort a #'<))
        a)
     =>  (1 2 3 4 6 7 FIVE)
     OR=> (2 1 4 3 7 6 FIVE)
     OR=> (2)
     
      (prog foo ((a (list 1 2 3 4 5 6 7 8 9 10)))
        (sort a #'(lambda (x y) (if (zerop (random 5)) (return-from foo a) (> x y)))))
     =>  (1 2 3 4 5 6 7 8 9 10)
     OR=> (3 4 5 6 2 7 8 9 10 1)
     OR=> (1 2 4 3)