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Date: Wed, 20 Feb 2008 07:53:19 +0200
From: Niklas Holsti <niklas.holsti@tidorum.invalid>
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Newsgroups: comp.lang.ada
Subject: Re: Is it really Ok to assert that the Ada syntax is a context-free
  grammar ?
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Date: 2008-02-20T07:53:19+02:00
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Hibou57 wrote:
> Hi peoples living here :p
> 
> I got a doubt about [ARM 1.1.4-1]
> 
>> The form of an Ada program is described by means of a
>> context-free syntax together with context-dependent
>> requirements expressed by narrative rules.
> 
> But as pointed by someone, the grammar is not LR(1), due to the fact
> (which is common to many other languages), that as an exemple X(Y) can
> stand for a type cast, a function call, an array access, or even an
> array slice, and this cannot be decided without knowlegde of the
> context.

So? I believe several programming languages are defined by 
context-free grammars that are ambiguous unless such "static 
semantics" is used to guide the parsing.

Trying to express all language rules in the grammar leads either to 
wild proliferation of punctuation symbols (as in some Basics or 
Perl) or to a context-dependent grammar (as in the Algol 68 
two-level grammar).

 > Am I wrong or is there really a so big mistake in the ARM ?

The ARM doesn't say that the grammar is LR(1), only that it is 
context-free, and that is true.

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
       .      @       .