"Khoa Nguyen" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
>
> for tokens,start,end in commaSeparatedList.scanString(data):
> print tokens
>
>
> This returns:
>
> ['f1', 'f2', 'f3', 'f4', 'f5', 'f6']
> ['f1', 'f2']
> ['f1', 'f2', '', 'f4', '', 'f6']
>
<snip>
> On 2nd thought, I don't think this will check for the correct order of
> the fields. For example, the following would be incorrectly accepted:
>
> f1,f5,f2 END_RECORD
>
> Thanks,
> Khoa
Well, what are the rules for the comma-separated entries? Are they
distinguished by type, or are they in ascending lexical or arithmetic order,
or by ascending length?
Two approaches you can take:
- if at parse time you can determine if f5 is out of position because it is
a specific type, then you can define your grammar like:
Optional(f1SpecificFormat) + "," + Optional(f2SpecificFormat) + "," + ...
and so on.
Then f5 would only match if in the fifth position.
Or, if even the commas are optional (as in f2,f5 END_RECORD), then you would
need a grammar such as:
Optional(f1SpecificFormat) + Optional(Optional(",") + f2SpecificFormat) +
... + "END_RECORD"
- if f5 is out of order because it is followed by f2, but would have been ok
if followed only by f6-fN values, then you'll need to read everything in,
and then test for validity, most easily in a parse action. If the
validation rule fails, then have the parse action raise a ParseException, so
that the match would be rejected.
-- Paul
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