dissect error on semi-dual

[Jörg Sommrey]

Hi all,

I'm new to J and this forum, so please excuse me if this question has
already been answered elsewhere.

Trying to dissect a phrase containing a semi-dual results in an error message:

]bl =. (<3 2 1),(<'c';'b';'a')
┌─────┬───────┐
│3 2 1│┌─┬─┬─┐│
│ ││c│b│a││
│ │└─┴─┴─┘│
└─────┴───────┘
1 0 1 #&.(a:`>) bl
┌───┬─────┐
│3 1│┌─┬─┐│
│ ││c│a││
│ │└─┴─┘│
└───┴─────┘
dissect '1 0 1 #&.(a:`>) bl'
domain error: operands to &. must be verbs

Is this my error or dissect's?

Best regards,
-jo

[Marcin Żołek]

Hi,
This message shows up because semi-duals aren’t supported in Dissect
yet. It would probably be clearer if it said 'dissect restriction'
rather than 'domain error'. Thank you for the report, update is coming
soon :-)

Marcin

> To unsubscribe from this group and stop receiving emails from it, send
> an email to forum+un...@jsoftware.com.

[Jörg Sommrey]

Thank you! A great tool for a great language.

-jo

On Sun 01 Feb 2026 01:41:04 PM CET, Marcin Żołek

[Henry Rich]

Dissect was written approximately when the J release was 8.2.  The
language has changed a bit since then. Marcin Żołek is in charge of
Dissect now; he has fixed most of the old stuff that was broken by
changes through 9.6, and plans, as time permits, to support the new
features that have been added.

Henry Rich