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Postings from September 2023
On Sun, Sep 03, 2023 at 11:48:14AM +0300, Ivan Vorontsov wrote:
> With perl v5.38.0 I wrote a code similar to:
> perl -E 'sub foo ($x, $y //= 42, $z) {} foo(1, undef, 3)'
> and got the error:
> Mandatory parameter follows optional parameter at -e line 1, near "$z) "
>
> So //= and ||= mark a parameter as optional, but optional parameters
> must follow mandatory ones. Outside of signatures these operators check
> a value of a variable. A mandatory parameter can have undef or false
> value. If it is feasible, maybe these operators could be applied to
> mandatory parameters as well.
I don't see how that could work. It makes for an ambiguity.
You could create a parser rule which says that that if a mandatory
parameter follows a ||= parameter, then the ||= should be interpreted as
mandatory and vice versa:
sub f1($x, $y ||= 1, $z) {...} # $y is mandatory
sub f2($x, $y ||= 1, $z = 1) {...} # $y is optional
but then this becomes ambiguous:
sub f3($x, $y ||= 1) {...} # is $y optional or mandatory?
--
Please note that ash-trays are provided for the use of smokers,
whereas the floor is provided for the use of all patrons.
-- Bill Royston
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