Re^3: Distinguish between missing and undefined arguments with subroutine signatures


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Re^3: Distinguish between missing and undefined arguments with subroutine signatures

by choroba (Cardinal)

on Dec 27, 2020 at 18:08 UTC ( [id://11125804]=note: print w/replies, xml )

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in reply to Re^2: Distinguish between missing and undefined arguments with subroutine signatures
in thread Distinguish between missing and undefined arguments with subroutine signatures

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]