Re: Is this grammar LL(1) ?

Hans-Peter Diettrich <DrDiettrich@compuserve.de>
22 Sep 2005 23:42:04 -0400

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Related articles
Is this grammar LL(1) ? sky4walk@gmx.de (2005-09-17)
Re: Is this grammar LL(1) ? DrDiettrich@compuserve.de (Hans-Peter Diettrich) (2005-09-22)
Re: Is this grammar LL(1) ? jjan@cs.rug.nl (J.H.Jongejan) (2005-09-22)
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From: Hans-Peter Diettrich <DrDiettrich@compuserve.de>
Newsgroups: comp.compilers
Date: 22 Sep 2005 23:42:04 -0400
Organization: Compilers Central
References: 05-09-064
Keywords: parse, LL(1)
Posted-Date: 22 Sep 2005 23:42:04 EDT

sky4walk@gmx.de wrote:


> i've a question about this grammar
>
> E->'a',F,A,F,'b'.
> F->'c',F | epsilon.
> A->'d',A_1.
> A_1->'d',A_1 | epsilon.
>
> is this grammar LL(1)?


IMO your grammar syntax is not very appropriate for LL(1), in detail
the epsilon's lead to confusion. Using an EBNF with optional elements
and recursion would be more appropriate instead. Have a look at
CoCo/R, for some more appropriate grammar representation.


I'd rewrite this grammar as:
E -> 'a' F A F 'b'.
F -> { 'c' }. //or F -> ('c')*.
A -> 'd' { 'd' }. //or A -> ('d')+.


DoDi

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