Patrick R. Michaud <[EMAIL PROTECTED]> wrote:
Does anyone have any suggestions about what sort of PIR
code and/or PMCs we need to be able to do make the following
Perl 6 code work...?
Sure. I think Tcl handles this pretty nicely at the moment (although
Leo disagrees - he likes the Ref PMC route). The main idea is that
aliasing/binding enters the same PMC under a different name and that
assignment morphs the PMC.
my @a;
@a[4] = 'Hello';
my $b := @a[4];
say $b; # says "Hello"
@a[4] = [1, 2];
say $b; # says "1 2"
Here are the pieces I can fill in:
#### my @a;
new $P0, .Perl6List
.lex '@a', $P0
#### @a[4] = 'Hello';
find_lex $P1, '@a'
# (in general case we autovivify @a here if needed)
set $P1[4], 'Hello'
#### my $b := @a[4];
find_lex $P2, '@a'
$P2 = $P2[4]
.lex '$b', $P2
#### say $b; # says "Hello"
say $b
#### @a[4] = [1, 2]
$P2 = 'list'(1, 2) # create a list
find_lex $P3, '@a'
# (in general case we autovivify @a here if needed)
set $P3[4], $P2
With this scheme, you'd have to use assign in this last case instead
of set (with a morph to really make it safe) because you need to reuse
the same PMC:
#### @a[4] = [1, 2]
$P2 = 'list'(1, 2)
find_lex $P3, '@a'
$P3 = $P3[4]
morph $P3, .Undef
assign $P3, $P2
If you're only assigning your own PMCs, you can drop the morph (which
isn't technically safe anyway).
--
Matt Diephouse
http://matt.diephouse.com
