Re: Multiple uses of (?{ code }) do not appear to be called

Yet another variant, which allows you to keep your original my @o.

The idea is to wrap a kind of "throw-away" subroutine around the push ... code. The subroutine is created anew every time the ?{...} code is being called.

sub foo {
    my $window = "a b X20 c X5 d e X17 X12";
    my @o;
    my @m = ($window =~ m/(X\d+(?{(sub {push @o, @_})->(pos)}))/g);
    print join(" ", "Matches:", @m, "\n");
    print join(" ", "Offsets:", @o, "\n\n");
}
[download]

It thus is working around the closure effect of "binding" the first instance of the dynamic variable @o to the ?{...} code.

(I'm not saying that this is in any way better than the other suggestions (in particular blazar's suggestion using our @o)... but heh, Perl would only be half as much fun if there weren't always more than one way to do it :)

Comment on Re: Multiple uses of (?{ code }) do not appear to be called Select or Download Code

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Re^2: Multiple uses of (?{ code }) do not appear to be called by bsdz (Friar) on Dec 29, 2006 at 15:48 UTC
I did try something similar using external anonymous subs but that didn't work. Interesting that it works if the sub is inline.	[reply]
Re^3: Multiple uses of (?{ code }) do not appear to be called by almut (Canon) on Dec 29, 2006 at 18:09 UTC
Thing is, if you declare the sub outside of the `?{...}` code, that code will bind the first instance of the subroutine. Printing the coderefs shows what's going on: `sub foo { my $window = "a b X20 c X5 d e X17 X12"; my @o; my $push_o = sub { push @o, @_ }; print "subN=$push_o\n"; my @m = ($window =~ m/(X\d+(?{print "sub1=$push_o\n"; $push_o->(po +s)}))/g); print join(" ", "Matches:", @m, "\n"); print join(" ", "Offsets:", @o, "\n\n"); }` [download] Output: `subN=CODE(0x8119060) sub1=CODE(0x8119060) sub1=CODE(0x8119060) sub1=CODE(0x8119060) sub1=CODE(0x8119060) Matches: X20 X5 X17 X12 Offsets: 7 12 20 24 subN=CODE(0x8131ac0) sub1=CODE(0x8119060) sub1=CODE(0x8119060) sub1=CODE(0x8119060) sub1=CODE(0x8119060) Matches: X20 X5 X17 X12 Offsets: subN=CODE(0x8119d50) sub1=CODE(0x8119060) sub1=CODE(0x8119060) sub1=CODE(0x8119060) sub1=CODE(0x8119060) Matches: X20 X5 X17 X12 Offsets:` [download] Despite three subroutines being created (--> "subN=..."), the one actually being called within `?{...}` is always the same, first one (--> "sub1=..."). This sub in turn is bound to the first instance of the variable `@o` ...	[reply] [d/l] [select]
Re^2: Multiple uses of (?{ code }) do not appear to be called by Anonymous Monk on Dec 30, 2006 at 06:41 UTC
There is an appreciation of this at http://use.perl.org/~jjore/journal/32016 I like it too. Unfortunately, on perl-5.8.3 I get a segmentation fault.	[reply]
Re^2: Multiple uses of (?{ code }) do not appear to be called by ikegami (Patriarch) on Mar 12, 2007 at 23:32 UTC
It's much easier, safer and faster to use package variables when dealing with regexps. `sub foo { my $window = "a b X20 c X5 d e X17 X12"; local our @o; my @m = ($window =~ m/(X\d+(?{ push @o, pos }))/g); print join(" ", "Matches:", @m, "\n"); print join(" ", "Offsets:", @o, "\n\n"); }` [download] Update: Oops, this has already been said elsewhere in the thread. I didn't enter this thread at the root node.	[reply] [d/l]