Re: Lazy/tolerant parsers

On 15 Jul 2004 16:35:08 -0400, Akhilesh Mritunjai wrote:


> "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote
>> Ada 95 expression parser and tree generator). The parser stops at
>> something it cannot recognize. At this point one can determine its
>> state. I.e. how many unclosed brackets, missing right operands etc you
>> have. One can use some kind of pattern matching to jump over an
>> indigestible part (not a name or literal, but just rubbish) and
>
> To where ?? That was the second part to my question.


To the next delimiter would be my first guess.


> From my parser I can get details of how and where the error
> happened. But still the questions of how to
> - recover from the error


Ideally there should be no other errors than "I do not understand the next
token". So you skip it and continue.


> - resynch


If you know the parser state, then you can take advantage of it. For
example, semicolon can close all open left brackets, always. "end;" should
close all "if", "case", "begin" etc.


> - continue parsing as if unaffected from error
>
> are open. Can't seem to find out a good solution to these problems.


--
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de

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