Instead of trying to solve this problem with magic regexs, another
possible solution to this is to try and solve it in the parser. For
example, you could have a grammar rule such as this:
def p_VECTOR(p):
"VECTOR : NUM"
if p[1] < 0 or p[1] > 1:
raise SyntaxError
p[0] = p[1]
The catch is that if the grammar uses NUM and VECTOR in
certain ways, you might get shift-reduce or reduce-reduce
conflicts (if not, all is well).
Cheers,
Dave
On Mon 05/01/09 1:13 AM , zt [email protected] sent:
>
> Hi Dennis,
>
> Thanks a lot.
>
> I totally ignore the priority part the lex at PLY documents.
> The only difference between NUM and VECTOR tokens are NUM always after
> some special words like TSET or repeat.
> I got a way to do this: t_NUM=r'(?<=TSET\s)\d+|(?<=repeat\s)\d+'
> only problem is (?<=) grammar only support fixed length so I can not
> use \s* to match the spaces between them. So another scan to sub all
> duplicated \s is needed.
>
> What would be the usually way to solve this kind problem: the same
> character at different locations meaning different TOKEN?
>
> Best Regards,
> Adun
>
> On Dec 31 2008, 5:32 pm, "Hendriks, D." <D.Hendr...@
> tue.nl> wrote:> Hello zt,
> >
> > both r'\d+' and r'0|1|...' match the numbers 0
> and 1. Since the r'0|1|...' regular expression has a longer length, it is
> given priority (see Ply documentation). Is there any way to differentiate
> the NUM and VECTOR tokens? For instance, can NUM tokens start with a 0 at
> all? You will need to have two regular expressions that only match the
> given input for that token (that is, no overlap). Well, you can have
> overlap, as long as you know it's there and the one that is given priority
> is the one you want to have priority, but still, I think it is better to
> avoid the overlap alltogether...>
> > Dennis
> >
> > ________________________________
> >
> > Van: ply
> [email protected] namens zt> Verzonden: wo 31-12-2008 9:49
> > Aan: ply-hack
> > Onderwerp: Lex token problem
> >
> > Hi all,
> >
> > I am still learning how to write parser with
> PLY. I need to parse> following format data:
> > TSET 1 001 X 0
> 00;>
> 001 X 0 00;>
> 001 X 0 00;> TSET 7 001 X 0
> 00;> repeat 12 001 X 0
> 00;>
> > The tokens are defined as:
> > t_TSET=r'TSET'
> > t_NUM=r'\d+'
> > t_MCODE=r'repeat'
> > t_VECTOR=r'0|1|H|L|X'
> >
> > but it kept treating the first "1" at
> line 1 as VECTOR instead of NUM> and the "1" after "repeat"
> as VECTOR.> Is there a good way to fix this?
> >
> > Thanks a lot!
> >
> > winmail.dat
> > 6KViewDownload
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