Example: ENQUEUE

Like PUSH, but puts the new element at the end of the list.

> (define-macro (enqueue item lst)

‘(if (null? ,lst) (set! ',lst '(,item))

(nconc ,lst (list ,item)) ) )

> (define q '(a b c))

> (enqueue 'd q)

> q

(A B C D)

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