Re: Possible bug with StringScanner class

--- John Halderman <jhalderman@xxxxxxxxx> wrote:

> On 7/22/05, Eric Mahurin <eric_mahurin@xxxxxxxxx> wrote:
> >
> > --- John Halderman <jhalderman@xxxxxxxxx> wrote:
> >
> > > I'm not sure if this is a bug or intentional behavior, so
> I
> > > thought I would
> > > post it here to see what the community thought of what
> was
> > > happening. If you
> > > set up a StringScanner object to perform iterative
> matching
> > > on a string the
> > > behavior of \A and ^ seem to always match. It seems to me
> > > that \A should
> > > only match if it is the first match performed, and ^
> should
> > > only match if
> > > bol? returns true, which should be after a \n or if it is
> the
> > > first match
> > > performed.
> >
> > You should think of the current position as the beginning
> of
> > the string for matching. In addition, the regexp that scan
> > gets is implicitly anchored to that spot. So specifiing \A
> or
> > ^ at the beginning of a regexp for scan is redundant.
>
>
> There is nothing in the documentation to suggest that the
> current position
> should be considered the beginning of a string for matching
> purposes, only
> that any match must start at that position. That would mean a
> regexp
> beginning with ^ would need the current position to be
> preceded by \n or be
> the at the beginning of the string in order for it to match.
> Furthermore,
> the existence of bol? suggests that the current position is
> not to be
> considered the beginning of the line. As for whether is
> should be considered
> the beginning of the string, that remains ambiguous, although
> I believe it
> makes more sense for it not to be so.

I think it makes perfect sense. scan/scan_until/etc only can
look at what is after the current position. They have no
visibility to what is before the current position. So, you
should consider it to be the beginning of the string for
matching purposes. Whether you like it or not, that is the way
it works and I think it is intentional.




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