On Thu, Aug 5, 2010 at 2:43 PM, Tyler Curtis <ekir...@gmail.com> wrote:
> On Thu, Aug 5, 2010 at 12:28 PM, Aaron Sherman <a...@ajs.com> wrote: > > While that's a nifty special case (I'm sure it will surprise me someday, > and > > I'll spend a half hour debugging before I remember this mail), it doesn't > > help in the general case (see my example grammar, below). > > In the general case, no. In the case of your grammar, and all > grammars, it does help. > > All regex routines, when called standalone, are anchored to the > beginning and end of the string. So, having "^" and "$" at the > beginning and end of your TOP is a no-op unless some other rule calls > it as a subrule. > There's something deeply disturbing to me in that... but I can't fully express what it is. It just feels like I'm going to end up debugging mountains of code, written by people who didn't understand that that was the case. Several times over the past few weeks, I've mentioned something on this list only to find that, buried somewhere deep in a synopsis, there was a special case I was unaware of. The sheer volume of silent special cases in Perl 6 appears to be dwarfing that of Perl 5, but perhaps that's just because I know Perl 5 far better than I know Perl 6. Mind you, I'm not complaining, so much as working out how I feel out loud.... Am I the only one who feels this way at this point? > :oneline or similar might be useful. I'm not sure about :rootedend and > :rootedstart. Are you saying that you can't think of examples of where you want to root a regex only to the start or end, or that you just don't think you need an adverb to do it? If the former, then I submit the 1536 examples of matching only at the end of strings in my local Perl library (mostly for matching whitespace or filename extensions it looks like) and the 3199 examples of matching only at the start which includes headers of all types (RFC2822 and friends, HTTP, CPAN configs, etc.), whitespace, command sequence matching (e.g. /^GET /) and so on. If the latter, then I guess you and I just have a different take, here, and that's fine. I respect your opinion, but in this case, I happen to disagree. PS: You can also search through any typical python install for "\.match" which will yield quite a lot of additional examples. I don't know Ruby or Java very well, or I'd go looking for examples there too. -- Aaron Sherman Email or GTalk: a...@ajs.com http://www.ajs.com/~ajs
