Feature request: builtin array holding ($1,$2,$3,...) #13412
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From @epaCreated by @epaIt would be useful to have a builtin array variable which holds the Suppose the builtin array is called @CAPTURE. Then $_ = 'abc'; There is a fair bit of boilerplate code with ($1,$2,$3,$4,$5) up to Perl Info |
From @HugmeirOn Tue, Nov 12, 2013 at 2:26 PM, Ed Avis <perlbug-followup@perl.org> wrote:
Eh, this looks like a feature better suited for CPAN. You can already package Capture { tie @CAPTURE, "Capture"; Although a proper implementation could avoid ties, I imagine. Also, rather |
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The RT System itself - Status changed from 'new' to 'open' |
From @demerphqOn 12 November 2013 20:11, Brian Fraser <fraserbn@gmail.com> wrote:
Ugh!
$1 is a tie itself. So @{^CAPTURE} would be a tie as well. The Yves -- |
From @demerphqOn 12 November 2013 18:26, Ed Avis <perlbug-followup@perl.org> wrote:
But there is: @CAPTURE= /(.)(.)(.)/ or die; IOW, in scalar context a regex match returns a list of items captured, Why would having a magic var for this be better? cheers, |
From @epaYves Orton wrote:
I mentioned one reason in the original report: in s/// you don't have access to this. Another reason is that m// in list context makes it hard to distinguish between a $_ = 'abc'; Both print '1'. So, if you have some code like if (/$re/) { do_something($1, $2, $3, $4, $5, ...) } there is not an obvious way to turn it into the form you suggest: @CAPTURE = /$re/; I am thinking of regular expressions which are specified in a configuration table, But if @CAPTURE were available as a builtin, you could simply say if (/$re/) { do_something(@CAPTURE) } -- ______________________________________________________________________ |
From @epaI would add that in general the reason to prefer an array @CAPTURE over individual $1, $2, $3 Similarly, think of @ARGV. We could do without that and instead have $ARG1, $ARG2, $ARG3 etc. In the case of @CAPTURE, the array would have to be read-only (so you can't shift it, etc) but Has nobody else here ever written code like foo($1, $2, $3, $4, $5)? And never wished there were -- ______________________________________________________________________ |
From @emazepOn 2013-11-15 11:55, Ed Avis wrote:
You can currently do: if ( my @CAPTURE =()= /$re/ ) { say @CAPTURE } P.S. Shouldn't be @CAPTURE spelled @CAPTURES? -Emanuele |
From @demerphqOn 15 November 2013 13:02, Emanuele Zeppieri <emazep@gmail.com> wrote:
Style preference. I tend to prefer to use singular for arrays where I if ($CAPTURE[1]) { } reads better to me than if ($CAPTURES[1]) { } Yves -- |
From @demerphqOn 15 November 2013 11:55, Ed Avis <eda@waniasset.com> wrote:
Color me convinced. :-) If FC doesnt beat me to it (as he so often does) I will add support for this. Let the debate begin about the name. I wont participate except to note @+ and then @CAPTURE(S) as well. I leave that for other to agonize over. Yves -- |
From @epaEmanuele Zeppieri wrote:
I don't think that works: $_ = 'abc'; For me this prints no -- ______________________________________________________________________ |
From @epaThank you Yves for offering to implement this. You can call it @BIKESHED if you want, and I'll still be delighted... -- ______________________________________________________________________ |
From @LeontOn Fri, Nov 15, 2013 at 11:19 AM, demerphq <demerphq@gmail.com> wrote:
Now if only we had array vtables, we could have implemented this in C Leon |
From @demerphqThe = () = is superfluous. Yves On 15 November 2013 13:08, Ed Avis <eda@waniasset.com> wrote:
-- |
From @hvdsEd Avis <eda@waniasset.com> wrote: I haven't, but I have frequently written code that makes the relevant array I'd rather see this prototyped on CPAN first, if only because IMO we have But I also feel that while the magic variable approach maybe made sense # assuming a new //mauve option that means "give me an object" (Sorry I haven't really been following this discussion, I'm in the middle Hugo |
From @epaI agree that a 'match object' might be a cleaner way to access properties of a regexp match. -- ______________________________________________________________________ |
From @demerphqOn 15 November 2013 15:19, Ed Avis <eda@waniasset.com> wrote:
I agree. We introduced %- and %+ without difficulty. I agree with hv -- |
From @emazep[Sorry for the private mail Ed, it was intended for the list] On 2013-11-15 13:08, Ed Avis wrote:
Indeed you are right, sorry again :-) However, give me a second attempt: $_ = 'abc'; sub test { sub f { say join '-', @_ } test qr/abc/; # match w/o captures: f is called with () What's the missing case? |
From ema.zep@libero.itOn 2013-11-15 13:02, Emanuele Zeppieri wrote:
No, it doesn't work, sorry! |
From @emazepOn 2013-11-15 13:08, Ed Avis wrote:
Indeed you are right, sorry again :-) However, give me a second attempt: $_ = 'abc'; sub test { sub f { say join '-', @_ } test qr/abc/; # match w/o captures: f is called with () What's the missing case? |
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From @emazepOn 2013-11-15 13:08, Ed Avis wrote:
Indeed you are right, sorry again :-) However, give me a second attempt: $_ = 'abc'; sub test { sub f { say join '-', @_ } test qr/abc/; # match w/o captures: f is called with () What's the missing case? |
From cm.perl@abtela.comLe 15/11/2013 11:55, Ed Avis a écrit :
this is a problem only it you don't know beforehand the number of
if (my @CAPTURE = /$re/) {
Again, can you provide an example ? I generally use either named capture my ($header, $param1, $param2); or named targets, as in if (my ($header, $param1, $param2) = m/..../) { @CAPTURE as proposed here strikes me as too rigid for me in most cases
--Christian |
From cm.perl@abtela.comLe 15/11/2013 11:55, Ed Avis a écrit :
You can always add a capturing group, for instance an empty lookahead : Taisha:~/tttmp $ perl -E 'for (@ARGV) { print; if (my @CAPTURE = --Christian |
From @emazepOn Fri, Nov 15, 2013 at 1:04 PM, demerphq <demerphq@gmail.com> wrote:
On a second thought, I see at least three points where you are right: 1. it's a question of style preference; |
From @emazepOn 2013-11-15 15:27, Ed Avis wrote:
Well, here is an alternative solution, which permits to save the $1 check The trick is to wrap the given regex in extra brackets: if ( my @CAPTURE = /($re)/ ) { do_something(@CAPTURE) } and then shift away the artificial capture in the called subroutine: sub do_something { (or before the sub call). Just to realize how much simpler it would be if your proposal were |
From @emazepOn 2013-11-16 00:21, Emanuele Zeppieri wrote:
And this further refinement avoids the shift too: if ( (undef, my @CAPTURE) = /($_[0])/ ) { do_something(@CAPTURE) }
No less ugly however (and potentially inefficient too), so the above is |
From @emazepOn Sat, Nov 16, 2013 at 1:10 AM, Emanuele Zeppieri <emazep@gmail.com> wrote:
Well, this avoids the potential inefficiency at least :-) if ( (undef, my @CAPTURE) = /()$_[0]/ ) { do_something(@CAPTURE) } |
From @tamiasOn Sat, Nov 16, 2013 at 12:21:18AM +0100, Emanuele Zeppieri wrote:
You should be aware that you cannot depend on any particular capture being $_ = "b"; if (my @CAPTURE = /$re/) { Ronald |
From @emazepOn Sat, Nov 16, 2013 at 6:46 AM, Ronald J Kimball <rjk@tamias.net> wrote:
The error was mine of course. However it's just a matter of finding a reliable indicator that a if ( my @CAPTURE = /$re/ ) { Does $#- > 0 serve the scope or are there exceptions? |
From @druud62On 2013-11-15 11:55, Ed Avis wrote:
@CAPTURE = m/$re/ and s//foo(@CAPTURE)/e But what if the g-modifier is used, AoA? perl -Mstrict -MData::Dumper -wle ' -- |
From @maukeOn 12.11.2013 18:26, Ed Avis (via RT) wrote:
Just FYI, that functionality is available as submatches() in Data::Munge. -- |
From @rjbs* hv@crypt.org [2013-11-15T08:44:17]
I agree. I threw this lousy code together a few months ago and it made me use strict; sub matches { return unless $str =~ $qr; $result->{capture_hash} = { %- }; bless $result, $class; sub capture { sub capture_list { sub captures { sub pre_match { sub match { sub post_match { 1; It would also be less surprising for programmers coming from just about -- |
From perl5-porters@perl.orgRicardo Signes wrote:
Why match? Why not just qr(...)->($str)? (Then we can forget smart-match altogether, since ->(...) is our match |
From @kentfredricOn 17 November 2013 09:53, Father Chrysostomos <sprout@cpan.org> wrote:
Maybe because it lends itself to later enhancements, ie: qr(...)->replace(sub{ }); May be nicer s{...}{ code }e; ( Especially seeing this syntax is more recognised by code -- |
From @tamiasOn Fri, Nov 15, 2013 at 02:19:38PM +0000, Ed Avis wrote:
Ronald |
From @epa
I'd be fine with that. It does remove the off-by-one oddity compared to $1, etc. -- ______________________________________________________________________ |
From @emazepOn Sat, Nov 16, 2013 at 12:01 PM, Emanuele Zeppieri <emazep@gmail.com> wrote:
Or rather: if ( my @CAPTURE = /$re/ ) { otherwise the case of a successful match but no matching subgroups Sorry for the noise! |
From @rjbs* Kent Fredric <kentfredric@gmail.com> [2013-11-16T16:16:46]
qr(..)->(...) does not rule out qr(...)->replace(...) -- |
From @demerphqOn 22 November 2013 04:21, Ricardo Signes <perl.p5p@rjbs.manxome.org> wrote:
The rules for parsing the right side of a regex are special cased. I fear adding support for the same special cases in a method call is s/(f)o(o)/$1$2/ how would you write that with method call notation without requiring qr/(f)o(o)/->replace("$1$2"); isn't going to work out of the box at all. Yves -- |
From @kentfredricOn 22 November 2013 20:55, demerphq <demerphq@gmail.com> wrote:
That would of course not work. It would have to be implemented in terms of qr/(f)o(o)/->replace(sub { Where internally, it did : s{(f)o(o)}{ $code->() }e At least, thats what I'd expect to be required given the current state Now maybe qr/(f)o(o)/->replace('$1$2'); Could be made work, just the surprisingness of that seems dangerous, -- |
From @kentfredricOn 22 November 2013 23:15, Kent Fredric <kentfredric@gmail.com> wrote:
Actually, on second thought, even that would not always be what you qr/(f)o(o)/->replace(sub { And that could lend itself to doing something like: $match->iterpolate("%1helloworld%2"); With the communicative property: if( my $result = qr/(f)o(o)/->match($string) ) { Essentially, making a sane way to pass state around from match results I don't really know, I must be tired or something. |
From @demerphqOn 22 November 2013 11:24, Kent Fredric <kentfredric@gmail.com> wrote:
Exactly. The delayed interpolation of the rhs of a s/// is hard to fit The only way to do so is require people pass in a closure. IMO hardly Yves -- |
From @epaI believe this has now been implemented as @{^CAPTURE} in perl 5.26 (thanks demerphq!) so the bug can be closed. |
From @jkeenanOn Fri, 09 Jun 2017 15:46:33 GMT, ed wrote:
Confirmed. ##### $ cat 120521-capture.pl $_ = 'abc'; $_ = 'def'; $ perl 120521-capture.pl Marking ticket Resolved. -- |
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@jkeenan - Status changed from 'open' to 'resolved' |
Migrated from rt.perl.org#120521 (status was 'resolved')
Searchable as RT120521$
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