Re: [SimpleParse] Graceful failure ?

[Mike C. F. <mcf...@ro...>]

H. T. Hind wrote:

>Hello, 
>
>Is there a way to get Simpleparse to gracefully exit instead
>of going into an infinite loop ? 
>
>For example if I have a grammar definition like this 
>
>column_specs := '<s>',ws,('<c>',ws)+,'\n'
>
>then the system would go into an infinite loop if the input
>contains '<S>' '<c>' 
>  
>
I don't see how it could with the given definition.  Infinite loops 
occur when you have a grammar like this:

column_specs := '<s>',ws,('<c>'?,ws)+,'\n'

that is, where you have a group that can match entirely with a null 
group and then you add an outer repeating modifier.  As defined, the 
engine allows for external parsers and the like which may, in fact, have 
a null-length match, so to catch this, would need to extend how 
mxTextTools communicates success/failure to allow for another state.

It's possible to catch it, yes, but it would require some considerable 
work to modify the engine to be able to support the feature.

Take care,
Mike

_______________________________________
  Mike C. Fletcher
  Designer, VR Plumber, Coder
  http://members.rogers.com/mcfletch/