Re: Help with Yacc++ ? (Mark A Biggar)
Wed, 12 Feb 1992 17:27:52 GMT

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Newsgroups: comp.compilers
From: (Mark A Biggar)
Keywords: yacc, errors
Organization: Loral Western Development Labs
References: 92-02-048
Date: Wed, 12 Feb 1992 17:27:52 GMT

In article 92-02-048 writes:
>I am having trouble with yacc++, an object oriented version of yacc put
>out by a company called Compiler Resources. ...
>I have a grammar
>S: E ;
>E: Id | -E | E-E | E E ;
>Can someone please tell me why yacc [LALR(1)] accepts this but
>yacc++ [LR(1)] doesn't.

Lets split you grammer up into separate productions like so:

S: E; (1)
E: id; (2)
E: -E; (3)
E: E-E; (4)
E: E E; (5)

What yacc++ is saying is that the input id-id-id is ambigious,
When it sees the second - it can't tell if it should reduce using
production (3) or (4).

Mark Biggar

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