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From: shebs@utah-cs.UUCP
Newsgroups: comp.lang.misc
Subject: Re: Programmable pretty-printers?
Message-ID: <4299@utah-cs.UUCP>
Date: Mon, 16-Feb-87 11:14:10 EST
Article-I.D.: utah-cs.4299
Posted: Mon Feb 16 11:14:10 1987
Date-Received: Tue, 17-Feb-87 05:47:04 EST
References: <1704@enea.UUCP>
Reply-To: shebs@utah-cs.UUCP (Stanley Shebs)
Organization: University of Utah CS Dept
Lines: 25

In article <1704@enea.UUCP> sommar@enea.UUCP(Erland Sommarskog) writes:

>A programmable pretty-printer (PPP) is an idea that's been in my head for a 
>while and I have been thinking that I should write one if I ever get the
>time.

This isn't a reference to a particular program, but Dick Waters' paper
"User Format Control in a LISP Prettyprinter" in the Oct 1983 TOPLAS
(vol. 5, no. 4) is about how to do it in a Lisp context (although the
idea could be applied to other languages).  The main idea is to decouple
formatting from printing and run each as a sort of coroutine.  The
interface is a stream of tokens, some of which represent literal objects,
others mark required line breaks, while still others mark optional breaks.
Then you have a user control that specifies how a given language construct
is to be broken into these tokens.  The specification syntax is a little ugly,
but you probably wouldn't want to use it directly anyway...  In any case, the
hard part of prettyprinting is counting columns and fitting stuff, and this is
handled by a module that doesn't need to know very much besides what to
do with tokens.

>Erland Sommarskog           sommar@enea.UUCP
>ENEA DATA, Stockholm

							stan shebs
							(shebs@cs.utah.edu)