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

[LanX]

> 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;
}

[jo37]

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.

[LanX]

> 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:

[LanX]

> 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.

[jo37]

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.