Re: [GNU-COBOL] COBOL Grammars and Parsers

[Chad Slaughter <slaught@babba.advancenet.net>]

Michael McKernan wrote :>
>
>>>>>> "Chad" == Chad Slaughter <slaught@babba.advancenet.net>
>>>>>> wrote the following on Thu, 15 Jul 1999 17:54:08 -0500 (CDT)
>
>  Chad> 2 separate machines.  machine 1: 4 processor 512MB ram, 4 GB
>  Chad> swap machine 2: 4 processor 4 GB ram, 16 GB swap
>
>While the PL/I preprocessor language is a lot smaller than COBOL,
>this never became an issue for me on much more modest machinery.

well, cobol is much larger adn it becomes an issue real quick.

>Ah. That's undoubtedly the reason.  I decided that small k means not
>greater than one.  I used syntactic predicate trial parses for

small k is less then 100. =)

>anything that couldn't be resolved with lookahead one and there
>actually didn't turn to be overly many cases that needed such
>predicates.  I actually felt that the parser was fairly compact.  My

well, cobol isnt that nice. you are welcome to try and change teh pccts
grammar to use syntactic predicates if you wish, i dont recall why we
didnt use tem.

>brief experiments with k > 1 resulted in parsers that I considered
>unmanageable and a quick glance at your makefile says that you were
>using k = 4.  

yes, thats the heart of the problem with pccts, cobol adn k=1, seems
next to impossible. or its more work then I really want to put in to it. =)

>I really think another alternative is k = 1 with syntactic
>predicates as tie-breakers.  I know, I know, I'm welcome to
>demonstrate that.

yes you are. =)

>Nor do I.  It was just a matter of not having the tools available on
>certain platforms.  It's no big deal if you have to do it, though.

must be for values of big deal, I was not previously aware of.

>Well, I know some stuff, I guess, but it ain't written down.  I'll

well, if you would write it down, it would be great.

>OK.  I'll at least try to find out how many rules break with k = 1.

i'll save you the trouble. all of them. now with syntactic predicates that
may be differnet, I dont know.

>It'll get worse.  I'm really a back end guy and have much stronger
>prejudices about other parts of the compiler. :-)

well, lucky for you, I am the only person you have to sway about the 
back-end of the system.



-- 
Chad Slaughter  -- slaught at advancenet.net

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