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Postings from January 2022
Dave, now that you've explained this, your proposal does seem by far the
simplest and backwards compatible option for named parameters, versus "real"
named parameters that I mentioned. -- Darren Duncan
On 2022-01-31 12:50 p.m., Dave Mitchell wrote:
> On Fri, Jan 21, 2022 at 09:38:41PM -0800, Darren Duncan wrote:
>> I know this isn't the main point of what you're saying, but I want to
>> address the matter of named arguments.
>>
>> Your example code using "=>" may have just been representative and not literal.
>>
>> But I want to argue that when/if Perl does add native support for named
>> parameters/arguments, which I hope it does, I feel that we must use a NEW
>> syntax to indicate it, and NOT use "=>".
>
>
> Just to be clear here. I fully expect that function calls will always
> consist of the caller passing a list to the function, and that the
> proposed named parameter syntax is just a way of easily processing
> adjacent pairs of values in that list. So in:
>
> sub foo(:$x, :$y) { ... }
>
> The caller is expected to pass 4 arguments. How the caller does this is up
> to the caller. They could do
>
> foo('x', 1, 'y', '2');
> @args = qw(y 2 x 1); foo(@args);
> foo(y => 2, x => 1);
>
> or even (as I suggest in a separate proposal)
>
> foo(=$x, =$y)
>
> where '=$VARNAME' is syntactic sugar for
>
> ('VARNAME', $VARNAME)
>
> and indeed can be used anywhere, not just in argument lists:
>
> @point = (=$x, =$y); # short for ('x', $x, 'y', $y);
>
> If anyone expects sub foo(:$x, :$y) {} to be anything other than the
> approximate equivalent of the following, please explain how you would make
> it differ.
>
> sub foo {
> croak unless @_ == 4; # actually a bit more subtle than that
> for (0,2) {
> croak unless $_[$_] =~ /^(x|y)$/;
> }
> my %args = @_;
> my ($x, $y) = @args{'x', 'y'};
> }
>
> and in particular whether named args can be called with non-name caller
> syntax, to allow modules to upgrade to signatures without affecting
> callers.
>
>
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