Re: About finding the start symbol of a grammar

From	"Ev. Drikos" <drikosev@gmail.com>
Newsgroups	comp.compilers
Subject	Re: About finding the start symbol of a grammar
Date	2021-05-22 06:52 +0300
Organization	Aioe.org NNTP Server
Message-ID	<21-05-019@comp.compilers> (permalink)
References	<21-05-015@comp.compilers>

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On 21/05/2021 13:49, Eduardo Costa wrote:
> While there would exist grammars we could recursively check to find out which
> it's start symbol is (i.e.: it's the only rule that used the rest of them,
> where checking every other resulted in dangling rules that weren't even called
> in), there might be other grammars for which more than one rule yields full
> coverage (all of these obviously defining different languages) and so leading
> to ambiguity.

IMHO, it can be so simple as you describe here without important overhead.
Typically, a parser will reduce the start symbol and finish. All rules
that yield full coverage can be ie alternatives of a single root symbol:

RootSymbol -> R1 | R2 | ... | Rn

Ev. Drikos

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About finding the start symbol of a grammar Eduardo Costa <ecosta.tmp@gmail.com> - 2021-05-21 03:49 -0700
  Re: About finding the start symbol of a grammar Kaz Kylheku <563-365-8930@kylheku.com> - 2021-05-21 14:14 +0000
    Re: About finding the start symbol of a grammar anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2021-05-21 15:32 +0000
  Re: About finding the start symbol of a grammar Hans-Peter Diettrich <DrDiettrich1@netscape.net> - 2021-05-21 17:02 +0200
  Re: About finding the start symbol of a grammar "Ev. Drikos" <drikosev@gmail.com> - 2021-05-22 06:52 +0300

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