From @masak

<clsn> r​: say <a b>.map({$_}) X, <c d>.map({$_})
<camelia> rakudo-parrot 58307f, rakudo-jvm 58307f​: OUTPUT«␤»
<clsn> What am I missing here? Shouldn't that be the same as <a b> X, <c d>?
<masak> r​: say (<a b>.map({$_}) X <c d>.map({$_}))
<camelia> rakudo-parrot 58307f, rakudo-jvm 58307f​: OUTPUT«␤»
<masak> r​: say (<a b> X <c d>)
<camelia> rakudo-parrot 58307f, rakudo-jvm 58307f​: OUTPUT«a c a d b c b d␤»
<jnthn> r​: say <a b>.map({$_})
<camelia> rakudo-parrot 58307f, rakudo-jvm 58307f​: OUTPUT«a b␤»
<clsn> I was going to try to use stuff like that to check for
subsetness among param names, but this cropped up.
<clsn> r​: say <a b>.perl; say <a b>.map({$_}).perl
<camelia> rakudo-parrot 58307f, rakudo-jvm 58307f​: OUTPUT«("a",
"b")␤("a", "b").list␤»
* masak submits rakudobug
<masak> r​: say (<a b>.map({$_}) X <c d>)
<camelia> rakudo-parrot 58307f, rakudo-jvm 58307f​: OUTPUT«a c a d b c b d␤»
<masak> interesting. so it takes two maps.
<clsn> r​: say (<a b> X <c d>.map({$_}))
<camelia> rakudo-parrot 58307f, rakudo-jvm 58307f​: OUTPUT«␤»
<clsn> No, only the second one it looks like.
<masak> oh!
<masak> yes.
<masak> clsn++
<masak> r​: say (<a b> X <c d>.map({$_})).perl
<camelia> rakudo-parrot 58307f, rakudo-jvm 58307f​: OUTPUT«().list␤»

From mark@kli.org

The problem is that the map is lazy and the X operator doesn't make it generate values​:

my $a=(1...3); my $b=(100...110).map({$_}); say $a X $b

my $a=(1...3); my $b=(100...110).map({$_}); my $c=$b[3]; say $a X $b
1 100 1 101 1 102 1 103 2 100 2 101 2 102 2 103 3 100 3 101 3 102 3 103

Note that once $b[0..3] are generated in order to put into $c, those elements--and only those--are available to the X op.

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

From @usev6

This works now​:

$ perl6 -e 'say <a b> X <c d>.map({$_})'
a c a d b c b d

$ perl6 -e 'say <a b>.map({$_}) X <c d>'
a c a d b c b d

$ perl6 -e 'say <a b>.map({$_}) X <c d>.map({$_})'
a c a d b c b d

I added tests to S03-metaops/cross.t with commit Raku/roast@d3aa62b272

I'm closing this ticket.

@usev6 - Status changed from 'open' to 'resolved'