[Jprogramming] Converting Conways Game Of Life from APL

[Ian Gorse]

Hi everyone,

I just been looking at a youtube video of Conways Games Of Life in APL
( http://www.youtube.com/watch?v=a9xAKttWgP4 )

And decided to follow it as much as I could in J. I have included the
time frame in NB. so you can fast foward the video yourself


NB. 0:47
R=. _1 _2 |. 5 7 {. r=. (3 3 $ i.9) e. 1 2 3 4 7

   R
0 0 0 0 0 0 0
0 0 0 1 1 0 0
0 0 1 1 0 0 0
0 0 0 1 0 0 0
0 0 0 0 0 0 0

NB. 1:00
   R;R;R
┌─────────────┬─────────────┬─────────────┐
│0 0 0 0 0 0 0│0 0 0 0 0 0 0│0 0 0 0 0 0 0│
│0 0 0 1 1 0 0│0 0 0 1 1 0 0│0 0 0 1 1 0 0│
│0 0 1 1 0 0 0│0 0 1 1 0 0 0│0 0 1 1 0 0 0│
│0 0 0 1 0 0 0│0 0 0 1 0 0 0│0 0 0 1 0 0 0│
│0 0 0 0 0 0 0│0 0 0 0 0 0 0│0 0 0 0 0 0 0│
└─────────────┴─────────────┴─────────────┘


NB. 1:14... surely there is a better way to do this??
   |: each 1 0 _1 |. each |: each R;R;R
┌─────────────┬─────────────┬─────────────┐
│0 0 0 0 0 0 0│0 0 0 0 0 0 0│0 0 0 0 0 0 0│
│0 0 1 1 0 0 0│0 0 0 1 1 0 0│0 0 0 0 1 1 0│
│0 1 1 0 0 0 0│0 0 1 1 0 0 0│0 0 0 1 1 0 0│
│0 0 1 0 0 0 0│0 0 0 1 0 0 0│0 0 0 0 1 0 0│
│0 0 0 0 0 0 0│0 0 0 0 0 0 0│0 0 0 0 0 0 0│
└─────────────┴─────────────┴─────────────┘

Now this is where I am stuck.
At 1:56 in the video, he creates 9 copies of R (3 3 $
R;R;R;R;R;R;R;R;R), and rotates each one using "outer product column
rotation"
(sorry I don't know how to explain it any better, so you will need to
check the video yourself)

Can someone please explain how this can be achieved in J?

Thanks