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Postings from March 2003
On Sun, Mar 16, 2003 at 09:37:51PM +0200, Enache Adrian wrote:
> On Sun, Mar 16, 2003 at 12:58:19PM +0000, Dave Mitchell wrote:
> > Perhaps bare regexs should be demoted to blocks and qr// should be
> > promoted to full anon sub status, so that they get cloned on each execution
> > of qr// ???
> >
> > Although I have to say that personally I don't like the idea of sharing
> > the same pad, simply becuase of run-time compilation, eg
> >
> > for (1..1_000_000) {
> > $p = '(?{my $x; ...})'; /$p/;
> > }
> >
> > This causes the pad to get filled with a million slots for defunct $x's.
> > Eval's have their own pad to avoid this sort of thing.
>
> I see three cases there - with their moral equivalent.
>
> 1. sub a { my $x; /(?{ $x++ })/ }
> => sub a { my $x; { $x++ } }
>
> 2. sub a { my $x; my $p = qr/(?{ $x++ })/; $_ =~ $p }
> => sub a { my $x; sub clos { $x++ }; clos }
>
> 3. sub a { my $x; my $p = '(?{ $x++ })'; /$p/ }
> => sub a { my $x; eval '$x++' }
>
> Does it look correct to you ?
yes, except for (2), which I would put as an anon sub so you get a new
closure for each execution:
2. sub a { my $x; my $p = qr/(?{ $x++ })/; $_ =~ $p }
=> sub a { my $x; my $p = sub { $x++ }; $p->() }
Whether it's practical to implement (1)..(3), and let alone what it would
do to backwards compatibility, I don't really have a feel for right now.
I'm also not certain whether it's fair on users to have (1) and (2)
implemented differently - that could cause suprises. eg does
my $x; $p = 'hello'; /$p(?{$x})/
get treated as case (1) or (2)?
(Disclaimer: I do bug fixes, not language design. Hence my general
vagueness here.)
--
"You're so sadly neglected, and often ignored.
A poor second to Belgium, When going abroad."
Monty Python - "Finland"
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