Perl6 RFC Librarian <[EMAIL PROTECTED]> writes:
> This has a dangerous and unpredictable side-effect which we would rather
> avoid. So the third and preferred candidate is:
>
> foo(x = 10, y = 20);
>
> In Perl 5 this is a syntax error raising a 'Bareword "x" not
> allowed...' error message. This is a Good Thing because it implies
> there aren't (m)any existing scripts that are currently using this
> construct.
sub x : lvalue { $x }
sub y : lvalue { $y }
foo(x = 10, y = 20);
However, I note that:
foo(x:10, y:20)
throws a syntax error, as does:
foo($x:10, $y:20)
Hey! So does:
foo($x := 10, $y := 20)
But that looks painful.
I also note that given
sub ($x, $y, $z) { #stuff
}
It might be nice if:
$curried_foo = foo(x:10, y:20);
returned an appropriately curried function... But Damian's already
doing curries elsewhere...
> RFC 9 proposes "Highlander Variables" in which C<$y> is implicitly a
> reference to C<%y> or <@y>. This would allow lists and hashes to be
> passed by reference as named parameters to the same effect. This is
> preferable to the above, (in the author's opinion) because the
> different types are more clearly disambiguated.
Note that, if the foo($x:1, @y:(1, 2, 3)) option is taken this removes
the 'requirement' for Highlander Variables, which in this author's
opinion can only be a good thing.
I would be inclined to argue that mixing named and positional calling
idioms should be a syntax error, or at the very least should trigger a
warning.
--
Piers
