Which context confuses this Perl 6 zip operator?

Question

Consider this program where I create a hash. I want to then change two values in it:

my $hash = %(
    wallet   => 100,
    gave     =>   0,
    received =>   0,
    );

for ^1 { $hash<wallet gave> Z+= <-1 1> };

dd $hash;

Like this, the last line of for doesn't do anything and there is no warning. The hash is unchanged:

Hash $hash = ${:gave(0), :received(0), :wallet(100)}

Adding another statement changes the behavior:

my $hash = %(
    wallet   => 100,
    gave     =>   0,
    received =>   0,
    );

for ^1 { $hash<wallet gave> Z+= <-1 1>; True };

dd $hash;

Now the inplace edit does its thing, but there's a warning (although I dispute "useless" when I've found a use for it):

Useless use of constant value True in sink context
Hash $hash = ${:gave(1), :received(0), :wallet(99)}

If I do without the Z+=, which should be the same thing, it works:

my $hash = %(
    wallet   => 100,
    gave     =>   0,
    received =>   0,
    );

for ^1 { $hash<wallet gave> = $hash<wallet gave> Z+ <-1 1> }

dd $hash;

Again the right output:

Hash $hash = ${:gave(1), :received(0), :wallet(99)}

That looks like a bug. Likely a sink context handling bug. `for ^1 { sink $hash Z+= <-1 1> };` or `for ^1 { say $hash Z+= <-1 1> };` both give the correct results. — raiph, Jul 10 '17 at 02:06
I had tried throwing sink in there and saw that it worked. Odd. — brian d foy, Jul 10 '17 at 04:20
FWIW, what version of Rakudo Perl 6 are you using? I recall a bug about not sinking the final value in a `for` loop being fixed quite recently. — Elizabeth Mattijsen, Jul 10 '17 at 12:47
Maybe related to this commit https://github.com/rakudo/rakudo/commit/acece7b2f7a8614c40d832a76ff67be2a71d851a — cuonglm, Jul 12 '17 at 04:45
I am still able to reproduce here: https://glot.io/snippets/evpyszdfgh — Felipe Valdes, Nov 22 '17 at 05:31

score 1 · Answer 1 · answered Feb 26 '18 at 18:23

1

It's a bug. Fixed as of Rakudo 2018.02.1-45-g8a10fc1

answered Feb 26 '18 at 18:23

Which context confuses this Perl 6 zip operator?

1 Answers1

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