That's awesome, and thank you. For posterity's sake, here's the string-eval
version I cooked up while refusing to give in to recursion:
t =: 1 2 3 ; <4 ; < 5 6; <7 8
n =: 123
addr =: 1 1 0
gener =: [:<')',[:,&'<t' '}'1}[:;[:,&'{>'&.>[:":&.>[:;/|.
". (;($addr)#<'(<') , 'n', ;|.gener\ addr
My hack: build up the nested, shelled } constructs, use some ugly >< that would
make anyone cry, and then eval it all. Hope it's helpful to someone else down
the road.
-----Original Message-----
From: Programming [mailto:[email protected]] On Behalf
Of Henry Rich
Sent: Wednesday, March 14, 2018 11:31 PM
To: [email protected]
Subject: Re: [Jprogramming] Question about updating boxed tree content
Yes, }:: is reserved for Emend which will do what you want. Someday. Maybe
erelong.
In the meantime, use applyintree from
http://code.jsoftware.com/wiki/Vocabulary/AmendingBoxedStructures
a =: 1 2 3 ; <4 ; < 5 6; <7 8
a
+-----+-------------+
|1 2 3|+-+---------+|
| ||4|+---+---+||
| || ||5 6|7 8|||
| || |+---+---+||
| |+-+---------+|
+-----+-------------+
(<123) [ applyintree (1;1;0) a
+-----+---------------+
|1 2 3|+-+-----------+|
| ||4|+-----+---+||
| || ||+---+|7 8|||
| || |||123|| |||
| || ||+---+| |||
| || |+-----+---+||
| |+-+-----------+|
+-----+---------------+
Henry Rich
On 3/14/2018 10:54 PM, [email protected] wrote:
> There's a question I'm tracking on Stack Overflow that I'm trying to solve:
>
> https://stackoverflow.com/questions/49288689/how-to-amend-data-in-a-bo
> x-j-pr
> ogramming
>
>
>
> Given a multi-level box:
>
> a =: 1 2 3 ; <4 ; < 5 6; <7 8
>
>
>
> How to you amend something given an address multiple levels into the
> box, e.g. the <5 6 part? I've tried some combination of S: and {:: and
> } however I can't seem to crack it. I might have expected this to work:
>
>
>
> (<123) (1;1;0)} a
>
>
>
> However, in this example, the (1;1;0) replaces item 1 and 0, treating
> the
> 1;1;0 as the list of elements to amend, as opposed to the array index
> to be amended, as is the case with (1;1;0) {:: a
>
>
>
> Does this mean that J needs a new amend operator, something akin to:
>
>
>
> (<123) (1;1;0) }:: a
>
>
>
> ?
>
>
>
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm
---
This email has been checked for viruses by AVG.
http://www.avg.com
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm
