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Postings from February 2012
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
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