Correctness of Transformations

It is not always easy to be certain that transformed code will give exactly the same results.

( (>  (* ?n ?x)
     (* ?n ?y))         (>  ?x ?y) )

( (not (not ?x))        ?x )

( (eq (if ?p ?qu ?qv)
      ?qu)              ?p )

( (rplaca ?x ?y)        (setf (car ?x) ?y) )

These transformations are ``usually'' correct, but it is possible to construct an example for each in which the transformation changes the result. We must be careful to use only correct transforms.

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