On Thu, 20 Apr 2017 08:39:41 -0700, cookbook_...@yahoo.co.jp wrote:
> See the following results:
>
>
> $ perl6 -e 'say (1..10).map({ { :a($_) } });'
> (a => 1 a => 2 a => 3 a => 4 a => 5 a => 6 a => 7 a => 8 a => 9 a =>
> 10)
>
> $ perl6 -e 'say (1..10).map({ ${ :a($_) } });'
> (-> ;; $_? is raw { #`(Block|57168408) ... } -> ;; $_? is raw {
> #`(Block|57168480) ... } -> ;; $_? is raw { #`(Block|57168552) ... }
> -> ;; $_? is raw { #`(Block|57168624) ... } -> ;; $_? is raw {
> #`(Block|57168696) ... } -> ;; $_? is raw { #`(Block|57168768) ... }
> -> ;; $_? is raw { #`(Block|57168840) ... } -> ;; $_? is raw {
> #`(Block|57168912) ... } -> ;; $_? is raw { #`(Block|57168984) ... }
> -> ;; $_? is raw { #`(Block|57169056) ... })
>
>
> I think the 2nd example should return the same result as the 1st
> example.
>
> $ perl6 --version
> This is Rakudo version 2017.03-217-ge681498 built on MoarVM version
> 2017.03-115-ge8231a3
> implementing Perl 6.c.
Thank you for the report, however this is not a bug.
In the first case, the bare block simply gets evaluated right away and its
result (a Pair) is returned. In the second case, you're itemizing that block,
so the block itself gets returned. You can achieve the same by, say, using a
pointy block, which also won't get evaluated right away:
say (1..10).map({ -> { :a($_) } });
(-> { #`(Block|58087136) ... } -> .... etc
I'm only guessing here, but I suspect you wanted the map to return a bunch of
1-element hashes? Like:
say (1..10).map: { %(:a($_)) };
({a => 1} {a => 2} {a => 3} {a => 4} {a => 5} {a => 6} {a => 7} {a => 8} {a
=> 9} {a => 10})
Note how I used the %() coercer instead of bare curlies. This is due to there
being an ambiguity in curlies: do they mean a block or a hash? When `$_`
variable is used inside, the compiler treats it as a block, which is why in
your case it evaluated the block or returned it when you tried to itemize it.
So another way to get a bunch of 1-element hashes is to not use the `$_`
inside, but some other variable:
say (1..10).map: -> $a { {:$a} };
({a => 1} {a => 2} {a => 3} {a => 4} {a => 5} {a => 6} {a => 7} {a => 8} {a
=> 9} {a => 10})
Cheers,
ZZ
