in terms of copying one node to another,
((1 ; 0)&{:: <@[ each amendT 0 ]) 0 ;<(< i.5);i.4
┌───────────┬─────────────────────┐
│┌─────────┐│┌───────────┬───────┐│
││0 1 2 3 4│││┌─────────┐│0 1 2 3││
│└─────────┘│││0 1 2 3 4││ ││
│ ││└─────────┘│ ││
│ │└───────────┴───────┘│
└───────────┴─────────────────────┘
to delete the original node (move)
{: each amendT 1 ((1 ; 0)&{:: <@[ each amendT 0 ]) (0 ;<(< i.5);i.4)
┌───────────┬─────────┐
│┌─────────┐│┌───────┐│
││0 1 2 3 4│││0 1 2 3││
│└─────────┘│└───────┘│
└───────────┴─────────┘
When I said tree processing is ok, I was thinking more of user trees rather
than "system trees" where the relationship among nodes is also user defined. I
should also point out that it is only ok after definining my own functions to
deal with trees.
and I will repeat that I agree that }:: (with compatible indexing to {::) would
be a big improvement, though the above uses a fairly simple workaround.
----- Original Message -----
From: Dan Bron <j...@bron.us>
To: programm...@jsoftware.com
Cc:
Sent: Monday, September 8, 2014 2:30 PM
Subject: Re: [Jprogramming] Ragged Array Shapes are Trees
Raul wrote:
> Note that J already supports trees.
Devon wrote:
> I have J code that uses trees which I run daily and
> have been doing so for years.
Pascal wrote:
> I think trees are done at least ok, if not "right" already.
Challenge: express, in J, the logic of rebalancing a heap (say, a Fibonacci
heap, but I'm not particularly picky).
For the sake of this exercise, you may ignore considerations of efficiency
(though that's a bit of a self-contradiction, because heaps are frequently
introduced specifically for the sake of efficiency). I am only interested
in the directness, simplicity, elegance (lyricality) of the notation, in
its current form, for expressing ideas about trees. We can make it
efficient "later" (Pepe's TCO utility is a start).
-Dan
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