On Mon, Nov 15, 2004 at 06:17:44PM +0000, Brian McCauley wrote:
> > I didn't mean to say that the behaviour is buggy.
>
> But, in fact, it is.
Er, no is isn't .... ;-)
> Let's see if I've got it straight.
>
> Currently AFAIK samples 1-5 below do the same thing.
>
> In a perfectly consitant world sample 4 should be an error.
No it shouldn't. The basic guiding principle is that if the code
is contained within a literal string, then you don't need use re 'eval'.
If it's the result of an expression, then it's suspect.
> Samples 1, 2
> and 5 should do the same thing but this may not be quite the same thing
> as sample 3 because in samples 1 and 2 $x should behave as if it is
> inside an eval(STRING) (as it is in 5) whereas in sample 3 it is not.
At the moment they behave as if they are within a hidden inner named sub,
which doesn't do the right thing most of the time. I want $x to behave as
if it's part of the enclosing sub. ie currently this fails:
sub foo { my ($x) = @_; /stuff...(?{ $x == something })..../ }
foo(1);
foo(2); # error - regex thinks $x is still 1
I want to it to behave scope- and closure-wise a bit like:
sub foo { my ($x) = @_; /stuff.../ && do { $x == something } && /..../ }
> Dave wants to correct the anomoly in the behavior of sample 3 wrt to the
> scoping of $x so that it does not behave as if it were inside string eval.
I want to fix 1-4, but have doubts about the best way to fix 1,2,4.
> However this is where things start to get confusing.
>
> One suggestion seems to be to change the behaviour of samples 1 and 4
> such they remain equivalent to sample 3. This would be wrong. Sample 1
> should remain equivalent to samples 2 an 5.
That was never the suggestion. My fallback plan if I couldn't come up with
anything better was to make 4 fail in the absence of a use re 'eval'; but
I think I can avoid that now.
> Another is that 1 and 4 should emit warings. This I would agree is
> probably a good idea.
Quite possibly.
> Sample 1
> use re 'eval';
> $foo =~ '(?{ $x = 1 })';
>
> Sample 2
> use re 'eval';
> my $re = '(?{ $x = 1 })';
> $foo =~ $re;
>
> Sample 3
> no re 'eval';
> $foo =~ /(?{ $x = 1 })/;
>
> Sample 4
> no re 'eval';
> $foo =~ '(?{ $x = 1 })';
>
> Sample 5
> no re 'eval';
> $foo =~ '(?{ eval q{ $x = 1 } })';
--
The warp engines start playing up a bit, but seem to sort themselves out
after a while without any intervention from boy genius Wesley Crusher.
-- Things That Never Happen in "Star Trek" #17
