Em Qua, 2009-05-20 às 19:55 -0500, John M. Dlugosz escreveu:
> If you would be so kind, please take a look at
> <http://www.dlugosz.com/Perl6/web/med-loop.html>. I spent a couple days
> on this, and besides needing it checked for correctness, found a few
> issues as well as more food for thought.
Some issues...
* The way to get an iterator is to ask for .Iterator() (this is in S07)
* It's not the capture itself that presents two different versions of
being a list, but rather the assignment in itself that traverses the
capture while flattening it.
i.e.:
my $x := map { $_ * 2 for 1,2,3 }, 1,2,3;
say $x[0]; # (1,2,3)
say $x[0;0]; # 1
say $x[1]; # (2,4,6)
say $x[1;0]; # 2
as a contrast to
my @x = map { $_ * 2 for 1,2,3 }, 1,2,3;
say @x[0]; # 1;
say @x[0;0]; # ERROR
say @x[1]; # 1;
say @x[1;0]; # ERROR
So, the list assignment really looks like
my $iterator = (map { $_ * 2 for 1,2,3 }, 1,2,3).Iterator();
my @x := Array.new;
while ((my $it = $iterator.get) !=== Nil) { @x.push($it) }
Where the map is consumes an iterator by itself, so you could expand it
as...
# this happens inside the &map function installed in CORE
my $map_input = (1,2,3).Iterator();
my $map_output = $MapIteratorInternalType.new(
:input($map_input),
:code({ $_ * 2 for 1,2,3 })
);
# this happens in the assignment
my $iterator = $map_output.Iterator();
my @x := Array.new;
while ((my $it = $iterator.get) !=== Nil) { @x.push($it) }
The text is fantastic... it's really awesome how you got into the guts
of Perl 6 while still preserving brevity and clarity...
daniel
