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Postings from October 2017
On Wed, Oct 25, 2017 at 11:48:23PM -0000, Father Chrysostomos wrote:
> Dave Mitchell wrote:
> > On Wed, Oct 25, 2017 at 03:40:15PM -0000, Father Chrysostomos wrote:
> > > If FETCH on a tied $x returns different values each time, does it con-
> > > tinue to behave the same way as currently?
> >
> > Yes - if a RHS arg is tied, it calls FETCH() for each appearance, and
> > makes a separate mortal copy of each result.
>
> Oh good. You seem to be anticipating my devilish attempts to find
> problems with your optimizations. :-)
I've tried very hard to be bug-for-bug compatible with existing behaviour.
See for example this code comment in pp_multiconcat()!
/* special-case $tied .= $tied.
*
* For something like
* sub FETCH { $i++ }
* then
* $tied .= $tied . $tied . $tied;
* will STORE "4123"
* while
* $tied .= $tied
* will STORE "12"
*
* i.e. for a single mutator concat, the LHS is
* retrieved first; in all other cases it is
* retrieved last. Whether this is sane behaviour
* is open to debate; but for now, multiconcat (as
* it is an optimisation) tries to reproduce
* existing behaviour.
But no doubt there will be a whole bunch of things I didn't anticipate,
and I look forward to the inevitable slew of BBC tickets.
--
My Dad used to say 'always fight fire with fire', which is probably why
he got thrown out of the fire brigade.
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