From: Antonio Romero
Subject: Disabling colons in CommonLisp
Date:
Message-ID: <2694@mind.UUCP>
I'm currently porting a production system from FranzLisp to Lucid CommonLisp
2.1.1 running on a Sun. I've run into a problem which I can't find a good
answer for, myself. What i need to be able to do is end certain keywords in
the productions with colons -- e.g. "action:" or "belief:".
My first thought was to try just making ":" into a macro character whose
associated function would return no values, so that colons effectively
disappear from the input stream. This worked for most purposes, but broke
things like "(member 'someatom somelist :test 'equal)" because ":test" was
no longer recognized as a keyword-- all lisp ever saw was "(member 'someatom
somelist test 'equal)."
My solution also made it impossible to reference symbols in other packages.
So I need a solution which would allow tokens to end in colons, without
breaking the other special interpretations associated with colons.
Ideally this would be possible within the CommonLisp standard, so as to be
portable, but I'll settle for a non-portable solution if I have to.
Has anyone out there solved this one already?
-Antonio Romero ······@confidence.princeton.edu
From: Barry Margolin
Subject: Re: Disabling colons in CommonLisp
Date:
Message-ID: <24747@think.UUCP>
In article <····@mind.UUCP> ······@mind.UUCP (Antonio Romero) writes:
>So I need a solution which would allow tokens to end in colons, without
>breaking the other special interpretations associated with colons.
>Ideally this would be possible within the CommonLisp standard, so as to be
>portable, but I'll settle for a non-portable solution if I have to.
>Has anyone out there solved this one already?
It will have to be non-portable, as there is no way to write what
colon does within Common Lisp. The problem is that the handler for
the colon character needs to back up the parser, and the Common Lisp
reader macro facility doesn't provide that functionality; reader
macros can only look ahead. Colon has to be built in to the reader so
that it can do this.
Couldn't you write an editor macro or sed script to go through your
production source files and put a backslash before the colons?
If you don't use colons for their Common Lisp meaning in the same
files as your productions then you could bind *READTABLE* to a
readtable that has colon defined as a constituent character while you
load the productions. When you are loading Lisp source files you
would use the regular readtable.
Barry Margolin
Thinking Machines Corp.
······@think.com
{uunet,harvard}!think!barmar