'From Squeak6.0 of 5 July 2022 [latest update: #22104] on 19 January 2023 at 11:33:58 am'!

!Form methodsFor: 'processing' stamp: 'spfa 1/19/2023 11:33'!
nextGeneration
	"Dan Ingalls Game of Life in BitBlt from Byte81 issue, see https://archive.org/details/byte-magazine-1981-08/page/n181/mode/2up and the following pages. "

 "
	|life|
	life := Form extent: 200@200.
	10000 timesRepeat: [life colorAt: 200 atRandom @ 200 atRandom put: Color black].
	[Sensor noButtonPressed] whileTrue: [
		life nextGeneration.
		(life magnifyBy: 4) displayAt: 10@50].
	Display restore.
"

	| ext carry2 carry4 nbr1 nbr2 nbr4 all n8 |
	ext := self extent + (2@2).
	nbr1 := Form extent: ext.	"ones bit of count"
	nbr2 := Form extent: ext. "twos bit of count"
	nbr4 := Form extent: ext. "fours bit of count"
	carry2 := Form extent: ext. "carry ones overflow into twos"
	carry4 := Form extent: ext. "carry twos overflow into fours"
	all := 0@0 corner: ext.
	
	n8 := {-2@ -1 . -2@ -2 . -1@0 . -2@0 . 0@ -1 . 0@0 . -1@ -2 . 0@ -2} .
	
	n8 do: [:offset |	
		"c2 := 1s & self"
		carry2 copy: all from: 0@0 in: nbr1 rule: Form over.
		carry2 copy: all from: offset in: self rule: Form and.
		"c4 := 2s & c2"
		carry4 copy: all from: 0@0 in: nbr2 rule: Form over.
		carry4 copy: all from: 0@0 in: carry2 rule: Form and.	
		"1s ^= self"
		nbr1 copy: all from: offset in: self rule: Form reverse. 
1 to: ext y do: [:h | nbr1 colorAt: 1 @ h put: Color black].		
		"2s ^= c2"
		nbr2 copy: all from: 0@0 in: carry2 rule: Form reverse.
		"4s ^= c4"
		nbr4 copy: all from: 0@0 in: carry4 rule: Form reverse.
	].
	"1s &= 2s"
	nbr1 copy: all from: 0@0 in: nbr2 rule: Form and.
	"self &= 2s"
	self copy: all from: 1@1 in: nbr2 rule: Form and.
	"self |= (1s & 2s)"
	self copy: all from: 1@1 in: nbr1 rule: Form under.
	"self &= !!4s"
	self copy: all from: 1@1 in: nbr4 rule: 4.
! !