Re: GenLex stream parsers too eager?

Date: Tue Jan 26 1999 - 20:17:54 MET

Date: Tue, 26 Jan 1999 13:17:54 -0600
Message-Id: <>
Subject: Re: GenLex stream parsers too eager?

>From: "David McClain" <>
>It appears that the Genlex derived parsers always eagerly tokenize =
>negaitve integer and float constants. This causes incorrect behavior in =
>closely spaced code (no-spaces):
> a-2*c --> parses as "a", "-2" ,"*", "c" instead of =
>So instead of getting one expression tree, I get two, with the first =
>containing only "a".
>Also, if the operator were exponentiation instead of multiplication, the =
>second tree would incorrectly compute a (possibly) complex valued =
>expression instead of a simple negative of a real expression.
>I have tried various workarounds, but they really obfuscate the original =
>recursive descent structure of parsers.
>Any suggestions? (Perhaps I should be using OCAMLLEX and OCAMLYACC =

I'd certainly suggest not using Genlex except for only the most trivial
things. Ocamllex and ocamlyacc are not difficult and they're much more

>David McClain
>Sr. Scientist
>Raytheon Missile Systems Co.
>Tucson, AZ

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