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From: mouse@mcgill-vision.UUCP
Newsgroups: comp.lang.misc
Subject: Re: The simplest way I know to PrettyPrint
Message-ID: <667@mcgill-vision.UUCP>
Date: Sat, 28-Feb-87 02:34:43 EST
Article-I.D.: mcgill-v.667
Posted: Sat Feb 28 02:34:43 1987
Date-Received: Tue, 3-Mar-87 19:48:18 EST
References: <366@esunix.UUCP>
Organization: McGill University, Montreal
Lines: 27

In article <366@esunix.UUCP>, bpendlet@esunix.UUCP (Bob Pendleton) writes:
> The  trouble  with  most  pretty printers is that they try to get too
> fancy. There is a fairly simple way to write a "programmable" pretty
> printer. The trick is to use the keywords and punctuation symbols of
> the language to trigger a set of actions in the pretty printer.

> [basically, scan tokens and do things as you get them]

> For instance the entry for "IF" might be something like.
> 	NextLine;
> 	Indent;
> 	WriteToken;
> 	IncrementIndent( 2 );

Except that this technique loses comments and formatting in the input.
Doing the right thing with comments can be difficult.  Doing the right
thing when breaking expressions over multiple lines can be very
difficult and in some cases impossible (eg, "len1+len2 + extra+1" versus
"len1 + len2+extra + 1" - how do you tell which + signs should have
spaces around them?  It depends on how they group conceptually.).

					der Mouse

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