Re^2: two regexes in one function call

I'm not sure that's the complete explaination as you get different results if you reverse the order of the statements:

#! perl -sw
use 5.010;

$data = do { local $/ = undef; <DATA> };

my $x = [
        scalar($data =~ s/(\w+)/$1/g),
        scalar($data =~ s/\n/\n/g),
];

say "@$x";

my $y = [
        scalar($data =~ s/\n/\n/g),
        scalar($data =~ s/(\w+)/$1/g),
];

say "@$y";

__DATA__
Line1 Word Something
Line2 Other Word
[download]

Gives:

c:\test>783947.pl
6 2
6 6
[download]

(Plus tr isn't a regex!)

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

RIP PCW

Comment on Re^2: two regexes in one function call Select or Download Code

Replies are listed 'Best First'.
Re^3: two regexes in one function call by ikegami (Patriarch) on Jul 28, 2009 at 16:56 UTC
Minor change: `#! perl -sw use 5.010; $data = do { local $/ = undef; <DATA> }; my $x = [map \$_, scalar($data =~ s/(\w+)/$1/g), scalar($data =~ s/\n/\n/g), ]; say "@$x"; my $y = [map \$_, scalar($data =~ s/\n/\n/g), scalar($data =~ s/(\w+)/$1/g), ]; say "@$y"; __DATA__ Line1 Word Something Line2 Other Word` [download] `SCALAR(0x2392c4) SCALAR(0x239224) SCALAR(0x239314) SCALAR(0x239314)` [download] The Ys use the same variable for the return value, but not the Xs. I don't actually know why the two calls return the same variable. Interestingly, the problem goes away if the captures are removed. Update: There has been a change in the relevant code since 5.10.0, but it appears to be an optimisation and not a fix. 5.10.0: `PUSHs(sv_2mortal(newSViv((I32)iters)));` maint-5.10 as it stands right now: `mPUSHi((I32)iters);` Patch In both case, it looks like the operator always returns a new SV, so maybe there's some stack corruption??	[reply] [d/l] [select]

Replies are listed 'Best First'.

Re^3: two regexes in one function call
by ikegami (Patriarch) on Jul 28, 2009 at 16:56 UTC

#! perl -sw
use 5.010;

$data = do { local $/ = undef; <DATA> };

my $x = [map \$_,
        scalar($data =~ s/(\w+)/$1/g),
        scalar($data =~ s/\n/\n/g),
];

say "@$x";

my $y = [map \$_,
        scalar($data =~ s/\n/\n/g),
        scalar($data =~ s/(\w+)/$1/g),
];

say "@$y";

__DATA__
Line1 Word Something
Line2 Other Word
[download]

SCALAR(0x2392c4) SCALAR(0x239224)
SCALAR(0x239314) SCALAR(0x239314)
[download]

The Ys use the same variable for the return value, but not the Xs.

I don't actually know *why* the two calls return the same variable.

Interestingly, the problem goes away if the captures are removed.

Update: There has been a change in the relevant code since 5.10.0, but it appears to be an optimisation and not a fix.

5.10.0:
PUSHs(sv_2mortal(newSViv((I32)iters)));

maint-5.10 as it stands right now:
mPUSHi((I32)iters);

Patch

In both case, it looks like the operator always returns a new SV, so maybe there's some stack corruption??

[reply]
[d/l]
[select]