Juerd wrote:
> Ingo Blechschmidt skribis 2005-11-20 16:44 (+0100):
>> Where is the difference (for the user) between a subroutine which
>> returns an appropriate proxy object and an array?
> The big difference between pure arrays and referenced arrays, for the
> user, is that pure arrays flatten in list context, while referenced
> arrays do not. Especially with for, this is very relevant.

I'd formulate this as "that @-arrays, i.e. variables whose sigil is @,
flatten in list context, while $-arrayrefs do not".

> I don't know if it is possible for an object to flatten in list
> context, but I would be surprised if it turned out to be.

For sure it is! Recall that "my @array = <a b c>" creates an object.

> Scalars should NEVER flatten in list context.

Yep. Again, I'd formulate this as "variables whose sigil is $ should
NEVER flatten in list context".

> This includes all references


> and thus objects.

I disagree -- @array and %hash, created by plain old assignment ("my
@array = <a b c>", "my %hash = (...)"), are objects.

>> I think it'd even optimize many cases:
>>     for @foo ¥ @bar {...}
> All for-optimizations are in the for, in Perl 5. It would be nice to
> have these in the actual functions and operators in Perl 6. Then
> for-reverse is not a special case anymore, and the optimization is
> indeed optimizing other cases too.

Yep. Also note that "for" is not a special magical construct in Perl 6,
it's a simple subroutine (&statement_control:<for>, with the signature
([EMAIL PROTECTED], Code *&code)). (Of course, it'll usually be optimized.)


        my sub statement_control:<for> ([EMAIL PROTECTED], Code *&code) {
            map &code, reverse @array;

        for <a b c> -> $item { say $item }
        # "c\nb\na\n"

    # for restored, as the modified for went out of scope:
    for <a b c> -> $item { say $item }
    # "a\nb\nc\n"

>> (BTW, IIUC, per r6622 of S06.pod [1] &zip returns an array of
>> arrayrefs now:
>>     for zip('a'...; 0...; @foo) -> [$a, $i, $x] { ...}
> Hm, that's sufficiently ugly. Is this really needed?
> I quite like how
>     for @foos Y @bars -> $foo, $bar { ... }
> looks, and don't quite like
>     for @foos Y @bars -> [ $foo, $bar ] { ... }
> as much.

I agree completely.

>> (Or does for no longer automatically take as much elements from the
>> input array as needed?
> I like the arity-sensitivity solution better, I think.

Me too. 


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