3. car. car[x] is defined if and only if x is not atomic. car [(e1 · e2 )] = e1 .
Thus car [X] is undefined.
car [(X · A)] = X
car [((X · A) · Y )] = (X · A)
4. cdr. cdr [x] is also defined when x is not atomic. We have cdr
[(e1 · e2 )] = e2 . Thus cdr [X] is undefined.
cdr [(X · A)] = A cdr [((X · A) · Y )] = Y
5. cons. cons [x; y] is defined for any x and y. We have cons [e1 ; e2 ] =
(e1 · e2 ). Thus
cons [X; A] = (X A)
cons [(X · A); Y ] = ((X · A)Y )