Re^5: Distinguish between missing and undefined arguments with subroutine signatures (slurpy parameter)

> To my understanding it is needed for an optional value argument in a signature.

Ah ... I see. Using a slurpy parameter @settings will solve this and fits much better into your use-case.

from perlsub

After positional parameters, additional arguments may be captured in a slurpy parameter. The simplest form of this is just an array variable:
sub foo ($filter, @inputs) { print $filter->($_) foreach @inputs; }
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Cheers Rolf
_{(addicted to the Perl Programming Language :)

Wikisyntax for the Monastery}

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Re^6: Distinguish between missing and undefined arguments with subroutine signatures (semipredicate problem) by jo37 (Curate) on Dec 27, 2020 at 21:13 UTC
Using a slurpy parameter @settings will solve this and fits much better into your use-case. Sadly, it does not. I already considered this. It does not prevent the sub from being called with more arguments than allowed. Greetings, -jo `$gryYup$d0ylprbpriprrYpkJl2xyl~rzg??P~5lp2hyl0p$`	[reply]
Re^7: Distinguish between missing and undefined arguments with subroutine signatures (semipredicate problem) by LanX (Saint) on Dec 27, 2020 at 21:21 UTC
> It does not prevent the sub from being called with more arguments than allowed. hmm ... you are going to extremes now. :) so `->mutate(FIELD)` is a getter for FIELD `->mutate(FIELD,VALUE)` is a setter for FIELD `->mutate(FILED,VALUE,OTHER...)` shouldn't compile I think, in this particular case you can still apply a prototype of `($;$)` together with the signature `($field,@values)` At least theoretically, not sure if it's still implemented that way. UPDATE well not with methods, see other post: Cheers Rolf _{(addicted to the Perl Programming Language :) Wikisyntax for the Monastery}	[reply] [d/l] [select]
Re^7: Distinguish between missing and undefined arguments with subroutine signatures (methods with signatures?) by LanX (Saint) on Dec 27, 2020 at 21:39 UTC
> It does not prevent the sub from being called with more arguments than allowed. Wait a second.... If you are talking about compile-time checking a `->method` I'm pretty sure that this can't be done in dynamically typed languages like Perl. Like with prototypes I expect this only to be possible with normal subs. ( without static typing of the `$obj` it's impossible to tell which `->methods` are allowed, normal subs OTOH can be pre-declared.) And when doing a dynamic check at run-time, using a @slurpy array is just good enough. Cheers Rolf _{(addicted to the Perl Programming Language :) Wikisyntax for the Monastery}	[reply] [d/l] [select]
Re^8: Distinguish between missing and undefined arguments with subroutine signatures (methods with signatures?) by jo37 (Curate) on Dec 27, 2020 at 21:53 UTC
If you are talking about compile-time checking ... No, I'm not talking about compile-time checking. I want method call checking at runtime. My `sig_lexical` example does what I want, but I'm not sure if this is a legal usage. Greetings, -jo `$gryYup$d0ylprbpriprrYpkJl2xyl~rzg??P~5lp2hyl0p$`	[reply] [d/l]
Re^9: Distinguish between missing and undefined arguments with subroutine signatures (methods with signatures?) by LanX (Saint) on Dec 27, 2020 at 21:59 UTC

UPDATE