thanks, fixed missing DOMAIN ERROR in SVN 1348.
Best Regards,
Jürgen
On 9/22/20 10:44 AM, Kacper Gutowski
wrote:
On Mon, Sep 21, 2020 at 01:17:18PM +0800, Elias Mårtenson wrote:
What is the neatest way to compute a Mandelbrot fractal in APL? The fact
that you have to break out of the loop as soon as the absolute value of Z
is >2 makes it a bit ugly. Is there a neater way to do this?
This is what I came up with that works in GNU APL:
" #"[⌊0.5+50÷⍨ { (n ⊣ {(x+⍵×⍵) ⊣ n←n+1}⍣{(2<|⍺) ∨ n≥50} n←0) ⊣ x←⍵ }¨
(0J1×r) ∘.+ r←¯2+25÷⍨⍳100]
If you wanted to use different colors for different number of iterations before it escapes 2≥| disc, my only suggestion would be to get rid of each which makes it slow. But since you only need one fixed threshold, I would do it like that:
rr←(0J1×r) ∘.+ r←¯2+25÷⍨⍳100
" #"[⎕IO+ 2≥| {⍺+×⍨⍵⊣((2<|,⍵)/,⍵)←2}⍣23⍨ rr]
(⍣23 instead of 25 because I start from ⍺ rather than from 0.)
Notably, if you use ⋆ with real right argument instead of ×, GNU APL has a bug where it returns infinity instead of a domain error, so you don't need to check for it ;)
" #"[⎕IO+ 2≥| {⍺+⍵⋆2}⍣23⍨ rr]
/cc Jürgen:
x←2⋆999
x⋆2 ⍝ should be a domain error
∞
x⋆2J0 ⍝ like it is here
DOMAIN ERROR
x⋆2
^^
-k
