On Tue, 2 Jul 2002, Michael G Schwern wrote:
> On Fri, Jun 28, 2002 at 01:21:50PM -0700, Erik Steven Harrison wrote:
> > Over on Perlmonks someone was asking about Perl 6's ability to have named
> > argument passing. He also asked about the Jensen Machine and Ruby iterators.
> > Now, just being on this list has taught me so much, but, I'm not quite sure
> > how it works, practically speaking, and whether or not we'll get in in P6.
> > (I understand the abstract o fpass by name, but not how we use it). Could
> > someone explain it to me, and tell me what the Perl 6 stance on the matter
> > is?
>
> * Yes, Perl 6 will have named arguments to subroutines.
>
> What I can remember from the Perl 6 BoF is it will look something like this:
>
> sub foo ($this, $that) {
> print $this if $that;
> }
> which is like:
>
> sub foo {
> my($this, $that) = @_;
> print $this if $that;
> }
>
> somebody else on this list can handle explaining how that all works better
> than I can. There's stuff about pointy subroutines, ->, method topics,
> etc... *hand wave*
>
Yep (far as I know. The only way I can secure my knowledge is to be
arrogant and then be confirmed or negated). After this, you can call foo
like so:
foo("Bar", 1);
Or like this:
foo(that => 1, this => "Bar");
Or like this:
foo("Bar", that => 1);
They all do the same thing.
As far as pointy subs, -> is just a synonym for sub, with some extra sugar
sprinkled on. You don't need to put parenthesis around the arglist, and I
think $_ is always aliased to the first argument. If there are no
arguments, the sub takes one argument and it is aliased to $_. Am I
right?
Of course you can't make named subs with ->, just anonymous ones.
> I *think* you will also be able to do this, at least I can't see why you
> wouldn't be able to:
>
> @stuff = grep { length $^foo >= 42 } @list;
>
> which is nice for nested greps and maps. You don't have to fight over who
> has $_.
Yep, grep takes a closure argument now. If you wanted to make things
interesting, you could do it this way too.
@stuff = grep -> $foo { length $foo >= 42 } @list;
> * Yes, Perl 6 will have the moral equivalent to Ruby iterators.
>
>
> Ruby also has it's |$a| mechanism to name the arguments. Presumably, you'll
> get the same effect with the implied arguments I mentioned earlier.
>
> File.foreach '/usr/dict/words' {
> print $^line;
> }
>
> Something like that.
Or
File.foreach '/usr/dict/words' -> $arg {
print $arg;
}
Luke
