predictive parsing

"j0mbolar" <j0mbolar@engineer.com>
19 Feb 2006 02:03:03 -0500

          From comp.compilers

Related articles
predictive parsing j0mbolar@engineer.com (j0mbolar) (2006-02-19)
Re: predictive parsing oliverhunt@gmail.com (oliverhunt@gmail.com) (2006-02-19)
Re: predictive parsing u.hobelmann@web.de (Ulrich Hobelmann) (2006-02-19)
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From: "j0mbolar" <j0mbolar@engineer.com>
Newsgroups: comp.compilers
Date: 19 Feb 2006 02:03:03 -0500
Organization: http://groups.google.com
Keywords: LL(1), parse, question

I am running into an issue with my LL(1) parser
in representing some of the nonterminals.


The problem is this:


suppose that I have the following grammar:


start: A B
A: C | C A | D | D A
B: '*'
C: '!' | '@'
D: 'X' | 'Y'


Where A, B, C, D are nonterminals
that are represented by functions.


The issue arises in representing the following production:
A: C | C A | D | D A


Imagine my initial lookahead token is '!'.
C() would be called and I would get my next
token. How then could I determine if A() should
be called or if the lookahead token applies to B,
where I should return and then call B?


I would also like to generate a syntax error
if the initial lookahead token does not follow
one of the rules of A.


I think this has to do with properly computing
what should be in the FIRST() set.


--
j0mbolar


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