Re: Distinguish between missing and undefined arguments with subroutine signatures

There is nothing like a missing argument with signatures:

#!/usr/bin/perl
use warnings;
use strict;

use experimental 'signatures';
use Syntax::Construct qw{ // };

sub show ($arg) { $arg // 'undef' }

use Test::More;
use Test::Exception;

throws_ok { show() } qr/Too few arguments/;

done_testing();
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map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]

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Re^2: Distinguish between missing and undefined arguments with subroutine signatures by jo37 (Curate) on Dec 27, 2020 at 17:41 UTC
My question was about optional arguments. Greetings, -jo `$gryYup$d0ylprbpriprrYpkJl2xyl~rzg??P~5lp2hyl0p$`	[reply]
Re^3: Distinguish between missing and undefined arguments with subroutine signatures by choroba (Cardinal) on Dec 27, 2020 at 18:08 UTC
Oh, sorry, I didn't get it. Why do you need it? It seems you don't want an optional argument with a default value, you want a subroutine that knows whether setting the default value was triggered. It's hard to do it with just the optional argument, as it's a single value, but you're interested in two values: the value itself and the boolean telling whether the default value was triggered. Both your solutions introduce such a value (whether it's the scalar @_ or the additional lexical variable). I'm not sure which one I'd prefer, but I'd probably add a comment to both of them. `map{substr$_->[0],$_->[1]\|\|0,1}[\\|\|{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^ARGV,3]`	[reply] [d/l]