From @masak

<masak> rakudo​: for [] -> $a { say $a.perl }
<p6eval> rakudo 7b0031​: OUTPUT«[]␤»
<masak> is this correct?
<masak> put differently, do things flatten in the <EXPR> position in
the for statement?
<TimToady> [] never flattens in a list
<TimToady> so it's correct
<masak> what about this one?
<masak> rakudo​: my %h = foo => []; for %h<foo> -> $a { say $a.perl }
<p6eval> rakudo 7b0031​: OUTPUT«[]␤»
<masak> I find I do such hash accesses when iterating on quantified
Match objects. I'd like to know if I should write %h<foo> or
%h<foo>.list in the for statement.
<masak> not least because bitrot in my code seems to indicate that the
behaviour changed in Rakudo recently :)
<TimToady> I think that one should flatten
<masak> what's the easy rule that distinguishes them?
<TimToady> there's no [] or $ to prevent it in the return from .<>
<masak> so... where there's no explicit "don't flatten" clue, the
thing flattens?
<TimToady> nod
* masak submits rakudobug

From @pmichaud

On Fri, Aug 20, 2010 at 03​:42​:57PM -0700, Carl Mäsak wrote​:

<masak> rakudo​: my %h = foo => []; for %h<foo> -> $a { say $a.perl }
<p6eval> rakudo 7b0031​: OUTPUT«[]␤»
<masak> I find I do such hash accesses when iterating on quantified
Match objects. I'd like to know if I should write %h<foo> or
%h<foo>.list in the for statement.
<masak> not least because bitrot in my code seems to indicate that the
behaviour changed in Rakudo recently :)
<TimToady> I think that one should flatten

Initially I disagree. Consider​:

  my %h = abc => [1,2,3], def => 4; for %h<abc def> -> $x { say $x.perl; }

I'd expect that loop to iterate twice, not 4 times.
In general, I think that .{ } and .[ ] on arrays and hashes
tend to produce scalar containers (which don't flatten by default).

To get an array in a hash element to flatten, I'd suggest @​%h<abc> .

TimToady can override this interpretation, in which case we'll
switch Rakudo to match. But I fear making hash and array elements
flattening by default will have far-reaching ramifications to other
things we're doing.

Pm

The RT System itself - Status changed from 'new' to 'open'

From @coke

On Fri Aug 20 17​:53​:36 2010, pmichaud wrote​:

On Fri, Aug 20, 2010 at 03​:42​:57PM -0700, Carl Mäsak wrote​:

<masak> rakudo​: my %h = foo => []; for %h<foo> -> $a { say $a.perl }
<p6eval> rakudo 7b0031​: OUTPUT«[]␤»
<masak> I find I do such hash accesses when iterating on quantified
Match objects. I'd like to know if I should write %h<foo> or
%h<foo>.list in the for statement.
<masak> not least because bitrot in my code seems to indicate that
the
behaviour changed in Rakudo recently :)
<TimToady> I think that one should flatten

Initially I disagree. Consider​:

my %h = abc => [1,2,3], def => 4; for %h<abc def> -> $x { say
$x.perl; }

I'd expect that loop to iterate twice, not 4 times.
In general, I think that .{ } and .[ ] on arrays and hashes
tend to produce scalar containers (which don't flatten by default).

To get an array in a hash element to flatten, I'd suggest @​%h<abc> .

TimToady can override this interpretation, in which case we'll
switch Rakudo to match. But I fear making hash and array elements
flattening by default will have far-reaching ramifications to other
things we're doing.

Pm

Sorry about the delay.

02​:53 < [Coke]> Here's another ticket that requires a ruling, and perhaps a
  rethink in the 3.5 years since it was opened​: RT #​77340
02​:58 < TimToady> given current understanding of how things itemize, I think Pm
  has it right, and we should reject the ticket
02​:58 < TimToady> except that @​%h<abc> can't work
02​:58 < TimToady> must be either @​(%h<abc>) or %h<abc>.list or %h<abc>[]

Rejecting ticket, sorry.

--
Will "Coke" Coleda

@coke - Status changed from 'open' to 'rejected'