On Monday 15 July 2002 11:22 pm, Deborah Ariel Pickett wrote:
> Besides, does
> $hashref = some_function_returning_a_hash()
> make $hashref simply refer to the result of the function, or does it
> make $hashref refer to a hash containing a *copy* of the result of the
> function? If Perl6 is going to do fancy things with functions returning
> lvalues, which looks like the case, those two things aren't necessarily
> the same thing.
I don't think scalar context can ever make copies of aggregate data. Here's a
little experiment.
sub func {
return a => 10; # returns a single pair; not a list or a hash
}
$foo = func(); # $foo is a PAIR ref, not a hash ref
$foo = { func() } # $foo is a CODE ref
$foo = { *func() } # $foo is still a CODE ref, I assume?
$foo = %{ func() } # die "Not a HASH reference"
$foo = hash func(); # This should work
> Or, saying the same thing another way, does this:
> $href = %hash;
> which I presume will be legal Perl6, mean the same as this Perl5:
> $href = \%hash; #A
It always means A according to some apocalypse.
my %hash = (key => "bar");
sub foo {
return %hash;
}
$ref = foo(); # $ref = \%hash
%copy = foo(); # %copy = { %hash }
%alias := foo(); # \%alias == \%hash
%$ref = foo(); # ($ref = {}) = %hash
> or this Perl5:
> $href = { %hash }; #B
The ways I can think to do that are:
%$href = %hash; # autovivify $href = {}, then copy
$href = hash %hash; # Perhaps * flattening is required?
> and how would I say each of A and B in Perl6 unambiguously?
I don't much like the effects of using %$foo as an lvalue. Having a context
sigil clobber the value doesn't seem very perl5ish. Perhaps I have my
blinders on and don't see where Perl5 does that.
> Automatic referencing and dereferencing is all well and good, and it
> appears that it's here to stay in Perl6 (it's been in most Apocalypses),
> but I don't think anyone's actually sat down yet to thrash out exactly
> under what circumstances it happens.
I think the rule of auto-hashifying only when an explicit pair is found is
gonna be hard to swallow.
I still have my vote on %() as a hash constructor in addition to {}. :)
Ashley Winters
--
When you do the community's rewrite, try to remember most of us are idiots.
