Re: [Pyparsing] How can I determine if a fragment is valid?

[Andrew S. <agt...@ya...>]

Paul, 

Thanks for the quick reply. So far using pe.loc <
len(input) works for me. I'll reply to the list if I
can find a counter example. Can I count on loc
sticking around in the ParseException class?

Not to push my luck, but I've got a grammar question
too. I'm trying to define a grammar that uses a
skipTo(Optional(xxx)) and not having much success. Is
there a better way to go about this?

An example

select where foo = 1 and bar = 2 into result

I was hoping to end up with something like the
following:

into_clause = Keyword('into') + restOfLine

Keyword('select') +
skipTo(Optional(into_clause)).setResultsName('where_condition')

Is there a way to do this without forcing some
delimiters onto the where clause?

Thanks again for such a useful library.

-a.

--- Paul McGuire <pt...@au...> wrote:

> Andrew - 
> 
> You may be able to infer something like this based
> on the location of the
> raised exception.  For instance, consider this
> grammar:
> 
> grmr = Literal("A") + ( Literal("B") + Literal("C")
> | Literal("D") +
> Literal("E") )
> 
> A full match would require one of these input
> strings (with whitespace
> allowed, of course):
> 
> ABC
> ADE
> 
> So any of these partial strings would indicate that
> there could still be a
> match:
> 
> A
> AB
> AD
> 
> but they would raise a ParseException since they are
> not complete.  The
> thing to note is, that the loc field of the raised
> exception is equal to the
> length of the input string, telling you that the
> missing piece would be
> found at the end of what was given, but that the
> input so far did match the
> grammar.
> 
> By contrast, these strings are not partially valid:
> 
> B
> AC
> ABX
> 
> In these cases, the loc field of the raised
> exception is less than the
> length of the input string, telling you that the
> provided string is not a
> partial match.
> 
> This is a very simplistic example, you should test
> this idea a bit more
> thoroughly with your own specific grammar.  I
> haven't thought it through
> myself for more than about 10 minutes, so please let
> me know how it works
> out.
> 
> -- Paul
> 
> 
> 
> 



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