Front page | perl.perl5.porters |
Postings from January 2022
On Monday, 24 January 2022, 07:50:33 CET, Darren Duncan <darren@darrenduncan.net> wrote:
> I still oppose as wrong-headed the concept of using such sentinel default values
> to try and detect when no argument is passed. The only use of such default
> values is when you don't care to distinguish between users explicitly passing
> that value from them not passing anything. When you actually want to
> distinguish them not passing a value, DON'T use defaults, and instead use "@" to
> capture the list and test the list for presence of an element. -- Darren Duncan
Then how do we fix the issue? What we *want* to know is how many arguments were passed to a variadic sub. You have this as an earlier example:
sub signatured(@maybe_x) {
if (scalar @maybe_x > 0) {
# we were given an argument, which may or may not be undef
}
else {
# we were not given an argument
}
}
You've sort of turned @_ into @maybe_x and now you can pass 20 arguments to it, killing one of the strongest features of signatures. Both your example and @_ are to attempts to determine how many arguments were passed to a sub. Imagine if we had a $^NUM_ARGS variable (terrible name, though I think someone else suggested it):
sub name ( $self, $name=undef ) {
if ( $^NUM_ARGS == 2) {
$self->{name} = $name; # even if undef
}
else {
return $self->{name};
}
}
By decoupling the signature from knowing how many args are passed, the solutions is much cleaner and we can't pass 20 arguments to the sub.
Best,
Ovid
--
IT consulting, training, specializing in Perl, databases, and agile development
http://www.allaroundtheworld.fr/.
Buy my book! - http://bit.ly/beginning_perl
Thread Previous
|
Thread Next