Re: Parsing newbie -- recursion question (probably simple)

Des Watson <desw@sussex.ac.uk>
13 Nov 2005 22:05:02 -0500

          From comp.compilers
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Parsing newbie -- recursion question (probably simple) sonicsmooth@gmail.com (2005-11-12)
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Re: Parsing newbie -- recursion question (probably simple) DrDiettrich@compuserve.de (Hans-Peter Diettrich) (2005-11-13)
Re: Parsing newbie -- recursion question (probably simple) desw@sussex.ac.uk (Des Watson) (2005-11-13)
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From: Des Watson <desw@sussex.ac.uk>
Newsgroups: comp.compilers
Date: 13 Nov 2005 22:05:02 -0500
Organization: Compilers Central
References: 05-11-059
Keywords: parse
Posted-Date: 13 Nov 2005 22:05:01 EST

sonicsmooth@gmail.com wrote:


> I'm having trouble getting my head wrapped around recursion. If I have
> the following rule to generate a list of nodes:
>
> nodelist := nodelist node | node


Left recursion! Not good for a traditional top-down parser, I'm afraid.
    It's probably easiest here to think about rewriting this production:


nodelist := node {node}


defining a nodelist as a node followed by an arbitrary number of nodes.
    Then writing a top-down recogniser for this is much easier...


Des Watson

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