University
of Washington • CSE583 • D. Notkin © 2000
31
Yet another example
lAppend
two lists non-destructively
–Requires
a copy of the first list but not the second one
–Sharing
of list substructures is common and safe with no side-effects
l(define
(append x1 x2)
(if (null? x1) x2
(cons (car x1)
(append (cdr x1)
x2))))
(if (null? x1) x2
(cons (car x1)
(append (cdr x1)
x2))))