Path: utzoo!utgpu!watmath!att!dptg!rutgers!apple!usc!ginosko!uunet!yale!Duchier-Denys
From: Duchier-Denys@cs.yale.edu (Denys Duchier)
Newsgroups: comp.lang.lisp
Subject: Re: substitution in sequences
Message-ID: <71160@yale-celray.yale.UUCP>
Date: 30 Aug 89 23:38:46 GMT
References: <425@ai.cs.utexas.edu>
Sender: root@yale.UUCP
Reply-To: Duchier-Denys@cs.yale.edu (Denys Duchier)
Organization: Computer Science, Yale University, New Haven, CT 06520-2158
Lines: 25
In-reply-to: farquhar@cs.utexas.edu (Adam Farquhar)

In article <425@ai.cs.utexas.edu>, farquhar@cs (Adam Farquhar) writes:
> Is there an elegant way to perform substitutions in a sequence where
> the new item may be of a different length than the old item?  E.g.
> 
> (substitute-it "Common lisp, the Language" "CLtL"
> 		"The right function does not seem to be in CLtL.")
> =>
> "The right function does not seem to be in Common Lisp, the Language."
> 
> or (substitute-it "abc" "1" "10101") 
> =>
>  "abc0abc0abc"

How about:

(defun substitute-it (new old seq)
    (let ((i (search old seq)))
      (if (null i) seq
	  (concatenate (type-of seq)
             (subseq seq 0 i)
             new
             (substitute-it new old
                (subseq seq (+ i (length old))))))))

--Denys