Procedure NCONC

Destructively concatenate two lists by creating a pointer from the CDR of the last cons in the first list to the first cons of the second list.

> (define (nconc l1 l2)

(cond ((null? l1) ())

((pair? (cdr l1)) (nconc (cdr l1) l2))

(#t (set-cdr! l1 l2)) ) )

> (define lst1 '(a b c))

> (define lst2 ‘(d e f))

> (nconc lst1 lst2)

> lst1

(A B C D E F)

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