Re: LL1 program ???

Joachim Durchholz <>
3 Jul 1998 22:53:11 -0400

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From: Joachim Durchholz <>
Newsgroups: comp.compilers
Date: 3 Jul 1998 22:53:11 -0400
Organization: Compilers Central
References: 98-07-009
Keywords: parse, LL(1)

Aulas de Inform=E1tica wrote:
> I am looking for a tool for transforming any language (given its
> grammar) into an equivalent one in its LL1 form.

It is unlikely that such a tool exists, as there are lots of languages
that do not have an LL1 grammar (but do have a LALR grammar, or a
grammar for some other parsing method). LL1 is one of the more
restricted language sets.

Rules to transform some common non-LL1 constructs into LL1 ones exist
(such as eliminating left-recursion), but these more often than not
lead to "unnatural" grammars that have only a rather remote connection
to what's really going on (which has unpleasant consequences for
associating semantic actions, or for checking whether your LL1 grammar
is really describing the language that you want nothing more or less).

-- =

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