Re: LL(1) vs LALR(1) parsers

:>napi@ms.mimos.my says...
:>
:>What is this ?. I have used both LL & LALR based tools and this
:>experience has convinced me never to use an LALR tool again. The
:>trouble with LALR tools is simple. An LALR parser has no idea about
:>the context of the syntatic structure. Hence, this leads to two
:>massive problems. (1). Writing an LALR parser needs to be done with a
:>bottom up thought process which is unnatural (well it is for me
:>anyway). (2). The error detection has no idea of the context so it
:>can't select a natural recovery point and the error meesages produced
:>are consequently usually poor.
:>
:>In summary, LL error recovery is vastly better than LALR. ...




You must have had a very poor implementation. I've worked with a
LALR(k) parser and found it much better than the LL(k) junk over all.
Any parser must address the error recovery problem. My LALR gave a
list of expected tokens and a list a productions in progress. The
parse tables could actual be used to produce a insert or delete
current token to continue the parse. Even recursive decent parsers
have problems recovering if the problem is not addressed.




Ken Walter
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