On Thu, May 10, 2012 at 1:46 PM, Aai <agroeneveld...@gmail.com> wrote:
> The J contribution on Rosetta Code
> http://rosettacode.org/wiki/Runge-Kutta_method#J for subject is a loopy
> one. My goal is to change that into a more functional and J-ish one.
>
> Here's my attempt for that particular task:
>
> p4=: 1 :(':';'({:y)+6%~+/1 2 2 1*(x*[: u y+(*x&,@{:))/\.1 0.5 0.5,x*u y')
>
> rk4M=: 1 :0
> 'Y0 a b h'=. 4{. y
> (,.[:h&(u p4)@(,{:)/\.Y0,~}.)&.|. a+i.@>:&.(%&h) b-a
> )
>
> (fyp rk4 -: fyp rk4M) 1 0 10 0.001
> 1
As a minor point, I think I would change the definition of p4
to use the same definition format as rk4M
p4=: 1 :0
:
({:y)+6%~+/1 2 2 1*(x*[: u y+(*x&,@{:))/\.1 0.5 0.5,x*u y
)
But I do not have the time to focus on this one.
I hope I'm not overlooking anything important.
(I wonder if the parenthesized expressions deserve names?)
Thanks for tackling this!
--
Raul
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