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Postings from January 2022
On Fri, 21 Jan 2022 16:49:22 +0000 (UTC)
Ovid <curtis_ovid_poe@yahoo.com> wrote:
> I knew my 3VL discussion went over like a lead balloon, but I
> couldn't resist being cheeky ...
>
> use Unknown::Values;
>
> sub foo ($bar = unknown) {
> say is_unknown $bar ? "unknown" : "known";
> }
>
> foo();
>
> That prints "unknown", so if someone passed in `undef`, it will print
> "known" because someone explicitly assigned to it.
Wellsure but now you've just moved the goalpost - how to distinguish
foo(unknown);
foo();
Ultimately, this comes down to the fact that since it is trivially easy
in perl to distinguish the values left in the @x array in:
my @x = (undef); # or (unknown);
my @x = ();
The same easy distinction ought to be possible with subroutine
arguments. It always has been so far.
--
Paul "LeoNerd" Evans
leonerd@leonerd.org.uk | https://metacpan.org/author/PEVANS
http://www.leonerd.org.uk/ | https://www.tindie.com/stores/leonerd/
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