question8

gistfile1.txt

(define (substitute s old new)
    (define (helper val)
        (define (final-val val old-val new-val)
            (if (eq? val old-val)
                new-val
                val
            )
        )
        (if (list? val)
            (map helper val)
            (final-val val old new)
        )
    )
    (map helper s)
)