'From Squeak6.0 of 5 July 2022 [latest update: #22104] on 19 January 2023 at 1:01:45 pm'!

!Form methodsFor: 'processing' stamp: 'spfa 1/19/2023 13:01'!
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 zp np |
	ext := self extent + (4@4).
	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"
	zp := 0@0.
	np := -1 @ -1.
	
	nbr1 copyAllFrom: zp in: self rule: Form reverse. 
	
	{2@0 . 0@2} do: [:offset |	
		"c2 := 1s & self"
		carry2 copyAllFrom: zp in: nbr1 rule: Form over.
		carry2 copyAllFrom: offset in: self rule: Form and.
		"1s ^= self"
		nbr1 copyAllFrom: offset in: self rule: Form reverse. 
		"2s ^= c2"
		nbr2 copyAllFrom: zp in: carry2 rule: Form reverse.
	].
	 {1@0 . 0@1 . 2@1 . 1@2 . 2@2} do: [:offset |	
		"c2 := 1s & self"
		carry2 copyAllFrom: zp in: nbr1 rule: Form over.
		carry2 copyAllFrom: offset in: self rule: Form and.
		"c4 := 2s & c2"
		carry4 copyAllFrom: zp in: nbr2 rule: Form over.
		carry4 copyAllFrom: zp in: carry2 rule: Form and.	
		"1s ^= self"
		nbr1 copyAllFrom: offset in: self rule: Form reverse. 
		"2s ^= c2"
		nbr2 copyAllFrom: zp in: carry2 rule: Form reverse.
		"4s ^= c4"
		nbr4 copyAllFrom: zp in: carry4 rule: Form reverse.
	].	
	"1s &= 2s"
	nbr1 copyAllFrom: zp in: nbr2 rule: Form and.
	"self &= 2s"
	self copyAllFrom: np in: nbr2 rule: Form and.
	"self |= (1s & 2s)"
	self copyAllFrom: np in: nbr1 rule: Form under.
	"self &= !!4s"
	self copyAllFrom: np in: nbr4 rule: 4.
! !