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Postings from February 2012
On 02/05/2012 11:27 AM, Tom Christiansen wrote: > demerphq<demerphq@gmail.com> wrote > on Sun, 05 Feb 2012 18:55:22 +0100: > >> Please Tom, it is very difficult to discuss things that are a mass of >> pod extracts. Next time either render the POD and then paste it as >> text, or don't use POD at all. > > Guilty. Sorry. Yes, you're right. Am rushed. > >> tr/// has nothing to do with the regex engine, IMO it has no place in >> a discussion about regular expressions. > > I don't want people slingshotting around looking for where the devil the > /mxyzptlk modifiers get explain. > > The four (or five) pick-your-own-quotes pseudofunctions qr//, m//, s///, > and tr/// (and y///) are distinct from the others in taking modifiers in > the /mxyzptlk slot, whereas q//, qq//, qx//, and qw// do not. > > Also, all four (or five) of the flaggy PYOQ pseudofuncs can be found > using the =~ operator. Yes, even qr//, for all the good it'll do you. > > $ perl -E 'say "frobnitz" =~ qr/([AEIOUWY])/i' > o > > And s///'s /r modifier does exactly the same thing as tr///'s /r > modifier does. > > % perl -E 'say "frobnitz" =~ y/aeiouy/yuoiea/r' > fribnotz > > But I do understand that tr/// doesn't belong in a section on pattern > matching. Had to put it somewhere, though, and I just refused to move it > to a functions area or an operators area. Larry stuck this in there, > fess'ing up to the matter: > > The tr/// transliteration operator does not interpolate variables; it > doesn’t even use regular expressions! (In fact, it probably doesn’t > belong in this chapter at all, but we couldn’t think of a better place > to put it.) > >> 3. Modifiers which change the behavior of the substitution process. > >> /e /ee /r > > Wait, you mean the RHS not the LHS, right? That's why you > didn't mention /g and /gc, because they apply to s///'s LHS? > > But why mention /ee distinct from /e? It's not special. > You can have /eee and /eeee if you want. eeeeetc. > >> Erm, maybe, but personally I would not document it the way you did. It >> makes sense as documentation for the individual operators, but IMO the >> division I used is much closer to the internals. > > I figure people looking for what modifiers they can apply to > the flaggy PYOQ pseudofuncs should be able to find all those > collected into one place. > > The /dual things are so strange. They're a mutually-dependent > radio group where turning one on turns the others off. Highlander > options. > > We could use a better way to do things. I'd like to figure out a way to make > those real words in there, just just letters. (?x-i:foo) is fine and all, but > we're starting to burst at the seams -- hence my /mxyzptlk remarks. > > I find qr/PATTERN/msixpodual to be way out there, and adding in > m/PATTERN/msixpodualgc and it's just too much. Then we get to > (?adlupimsx-imsx) plus the alternate (?^alupimsx), and that's just > beyond the pale. > > Plus now those aren't even listed in the same order as the m//flags are, > so you can't have a dependable mnemonic. > > Might as well use /mxyzptlk after all, eh? > > --tom > Patches welcome!Thread Previous | Thread Next