User:Dan Bron/Snippets/PrettyPictures

Idea for the next puzzle to present: draw pretty pictures using

   require 'viewmat'
   PP =: 1 : 'viewmat@:(u [: | j./~@:i:)'   NB.  The original  +&.*:/~@:i:  is much slower
   f PP n

where f is some short, elegant J verb and n a positive integer. Examples:

	f	description	png @ n=60
1	>	filled in circle
2	= <.	hollow circle
3	<.@:]	Bullseye, delta-circumference = 1
4	m ([ * [: <. 0.5 + %~) ]	Bullseye, delta-circumference = m
5	2 | <.@:]	hard to describe; just try it with various n (10, 50, 100, 250)
6	0 = 5 | <.@:]	similar to above, but the concentric circles more discernable
7	+/\@:]	rainbow half-hyperbola, gradual descent.
8	(|. -@:,~ )~	rainbow full-hyperbola (inside-out circle)
9	(|. -@:,~@:-:)~	circle vs. hyperbola.
10	<./\	prism/double spectrum/double slit experiment/one dimensional circle
11	>./\	sunrise over the ocean
12	>./\@:]	acute rainbow
13	_1 o. ]	concentrate
14	1 o. ]	kinda like the m | <.@:] pictures
15	_1 <.@:o. ]	i c u
16	_1 >.@:o. ]	like the bullsyes, but delta-circumference isn't constant (the bands change widths)
17	[/\ _1 >.@:o. ]	LSD sunrise
18	100 | 1000 * ^.	concentric rainbows
19	100 | 1000 * ^.@:]	kindergarten
21	100 | 1000 * (%:2) ^. ]	fractal thingummy
22	[: ?. <.@]	paint splatter
23	,/@:e.@:<.@:]	DNA dance (n must be small -- try n=.20 and maximize the resulting plot window
24	=@:]	It's for Victory!
25	|:@:(]/.)@:]	valentine
26	|:@:(/: /.)@:]	louvre
27	|:@:(/:~/.)@:]	pyramid power
28	involte@:,~@:>:@:-:@:[ { ,@:]	modern art (definition of involute)
29	(- >./@:,)@:involute@:,~@:>:@:-:@:[ { ,@:]	modern art 2
30	!~	and in the darkness bind them
31	|~	compass
32	[ | !~	ring around the rosey
33	p..@:]	cold front
34	[: |.@:|: 100 | 1000 * ] %~ ({.~_,#)@:p..@:]	hallelujah
35	[: |: 100 | 1000 * p..	skipping stone