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From: raja@copper.ucs.indiana.edu (Raja Sooriamurthi)
Newsgroups: comp.lang.scheme
Subject: Re: how to write append from primitives?
Message-ID: <raja.675463240@copper>
Date: 28 May 91 20:40:40 GMT
References: <1650003@hpkslx.mayfield.HP.COM>
Sender: news@bronze.ucs.indiana.edu (USENET News System)
Organization: Indiana University
Lines: 11

On way would be 

(define append
  (lambda (lst1 lst2)
    (if (null? lst1)
	lst2
	(cons (car lst1)
	      (append (cdr lst1) lst2)))))

Small exercise: modify append to take the union of lst1 and lst2
(assuming that lst1 and lst2 are themselves sets -- no duplicates)