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Postings from November 2010
On Tue, Nov 30, 2010 at 10:34:36PM +0100, Dr.Ruud wrote:
> On 2010-11-29 10:22, Dave Mitchell wrote:
>> On Sun, Nov 28, 2010 at 05:16:28PM -0800, Father Chrysostomos wrote:
>
>>> I know this is what constant.pm used to use, but it causes a bug:
>>
>> What do you think is the bug? It seems to be behaving the way I expect.
>>
>>> $ perl -MO=Deparse -e' BEGIN{my $x = 5; *foo = sub(){$x}; $x=6} print foo'
>>> sub BEGIN {
>>> my $x = 5;
>>> *foo = sub () {
>>> $x;
>>> }
>>> ;
>>> $x = 6;
>>> }
>>> print 5;
>
> The compiler should patch the constsub at the '$x = 6' line.
If the compiler can detect that afterwards $x won't change - but you
need to be able to solve the halting problem to do that in general.
For instance,
BEGIN {
my $x = 5;
*foo = sub () {$x};
*bar = sub {$x = shift};
}
the compiler could only patch the constsub if it knows bar() won't
be called.
Abigail
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