Front page | perl.perl5.porters |
Postings from January 2022
Paul "LeoNerd" Evans skribis 2022-01-19 17:59 (+0000):
> * As a variant of the above; you can't even see the count of passed
> arguments in order to distinguish no-argument from being explicitly
> passed undef (or whatever the param default is)
> sub signatured($x = undef) {
> # impossible to distinguish signatured() from signatured(undef)
> }
A simple workaround is possible by introducing a new undef-like value that has this very specific purpose:
use Scalar::Util qw(refaddr);
use constant NONE => \do { my $x };
sub _provided($x) { ref($x) && refaddr($x) == refaddr(NONE) }
sub bar($self, $new = NONE) {
$self->{bar} = $new if _provided($new);
$self->{bar};
}
As checking arity for combined getter/setter methods is incredibly common, maybe it would make sense to have a very tiny module, maybe even core, that exports these, or to add them to Scalar::Util.
Of course, this depends on not using the constant for other purposes. I think that's mostly a matter of documenting that the behavior of any other use of the constant is undefined.
--
Met vriendelijke groet, // Kind regards, // Korajn salutojn,
Juerd Waalboer <juerd@tnx.nl>
TNX
Thread Previous
|
Thread Next