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From: barmar@think.com (Barry Margolin)
Newsgroups: comp.lang.lisp
Subject: Re: Is MAP meant to operate on strings?
Message-ID: <1991Feb23.220923.10748@Think.COM>
Date: 23 Feb 91 22:09:23 GMT
References: <1991Feb23.205613.14321@magnus.ircc.ohio-state.edu>
Sender: news@Think.COM
Organization: Thinking Machines Corporation, Cambridge MA, USA
Lines: 28

In article <1991Feb23.205613.14321@magnus.ircc.ohio-state.edu> murthy@magnus.ircc.ohio-state.edu (Murthy S Gandikota) writes:
>(map 'string #'(lamda (x) (if (equal x #\e) #\f)) "I want to replace e
>with f")
>
>==> Error:  ARG not a character 
>
>(this is all the error informatin my LISP machine displays)

Must not be a Symbolics Lisp Machine.  After I fix the misspelling of
"lambda", mine says:

Trap: The first argument given to the SYS:CHAR-LDB-INTERNAL instruction, NIL,
      was not a character.

The problem is that your function returns NIL when the character isn't #\e,
and NIL isn't a valid element of a string.  You should have it return its
argument:

	#'(lambda (x) (if (char-equal x #\e) #\f x))

By the way, you might want to replace this with SUBSTITUTE:

	(substitute #\f #\e "I want to replace e with f")
--
Barry Margolin, Thinking Machines Corp.

barmar@think.com
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