🚀 go-pugleaf

>In article <16559@mimsy.UUCP> I included the throwaway% line:
>>... At least, this is the only explanation I can see that we never
>			    ^^^^^^^^^^^^^^^^^^^^^^^^^^
>>argue whether Pascal's grammar is context free.
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% cf. Webster: `throw.away \'thro--*-.wa-\ n : a handbill or circular
  distributed free'; applied to writing (especially comic writing), it
  refers to a line with similar worth.
-----

In article <12778@watdragon.waterloo.edu> akwright@watdragon.waterloo.edu
(Andrew K. Wright) writes:
>The difference I see is that a C grammar that accepts undeclared typedef
>names destroys more of the structure of the grammar than a Pascal
>grammar that accepts undeclared variable names.  Consider the following
>C expression:
>
>	x = (a)(b);
>
>If "a" is a typedef name, then the right side is a cast.  If "a" is
>not a typedef name, then the right side is a function call.
>I dont believe similar situations exist for Pascal (corrections welcome).

I am not sure what you mean by `destroys more of the structure of the
grammar'.  It is ambiguous, and in particular it is an ambiguity of an
uncomfortable sort, quite unlike the shift/reduce ambiguity for if/then/else
which everyone resolves by taking the shift.  Yacc permits this reduce/
reduce conflict, but resolves it by taking the first grammar rule; we
want the parser to take the *appropriate* grammar rule, which is sometimes
the first and sometimes not.  So yacc unaided will not produce a
deterministic parser that does what we want.

BUT all this applies to constructing a deterministic LALR(1) parser,
which is not at all the same thing as having a context free grammar!
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris