In a message dated Thu, 3 Jan 2008, [EMAIL PROTECTED] writes:
+But these bindings I<do> autovivify:
my %hash;
my $val := %hash<foo><bar>;
my @array;
- my $obj = [EMAIL PROTECTED]; # $obj is a Capture object - see S02
+ my $cap = [EMAIL PROTECTED]; # $obj is a Capture object - see S02
+ my :($obj) := $cap; # @array[0][0] created here
I'm wondering about that last line there. Going by S02, I see:
* There is now a generalized adverbial form of Pair notation. The
following table shows the correspondence to the "fatarrow" notation:
Fat arrow Adverbial pair Paren form
========= ============== ==========
[...]
'' => $x :($x)
which looks like C<:($obj)>. So I was reading the line
my :($obj) := $cap; # @array[0][0] created here
as saying, "create an anonymous Pair, with $obj bound to its value, and
bind the Pair to $cap (causing $obj to be bound to the value portion of
$cap)".
But I was told on #perl6 that :($obj) refers to a Signature. If so, I
think the relevant passage in S02 for deciphering the syntax is:
A signature object (Signature) may be created with colon-prefixed
parens:
my ::MySig ::= :(Int, Num, Complex, Status :mice)
So in that case, $obj refers to... what? The variable's just been
created, so its value is undef, so it's equivalent to a one-arg Signature
with an undef item, and it's being used as an lvalue, so.... I don't
understand.
Also, someone on #perl6 said that the colon could be omitted with no
change in effect. I don't get that, either.
Given its use in the autovivification discussion in S09, the Pair idea
made sense to me, but the Signature explanation is very confusing. I'd
appreciate some help understanding it.
Trey
