From 1b2fd71fc643bc23119cf61ed045b5a163f9ff8e Mon Sep 17 00:00:00 2001
From: Vince Weaver <vince@deater.net>
Date: Sun, 27 May 2018 18:45:07 -0400
Subject: [PATCH] entropy: getting closer to working

---
 two-liners/Makefile    |  6 ++-
 two-liners/entropy.bas |  7 ++++
 two-liners/entropy.s   | 90 ++++++++++++++++++++++++++++++++++++++++--
 3 files changed, 99 insertions(+), 4 deletions(-)
 create mode 100644 two-liners/entropy.bas

diff --git a/two-liners/Makefile b/two-liners/Makefile
index fa22e2b6..1c0125d1 100644
--- a/two-liners/Makefile
+++ b/two-liners/Makefile
@@ -5,8 +5,9 @@ TOKENIZE = ../asoft_basic-utils/tokenize_asoft
 
 all:	entropy.dsk
 
-entropy.dsk:	ENTROPY
+entropy.dsk:	ENTROPY ENTROPY.BAS
 	$(DOS33) -y entropy.dsk BSAVE -a 0x0C00 ENTROPY
+	$(DOS33) -y entropy.dsk SAVE A ENTROPY.BAS
 
 ENTROPY:	entropy.o
 	ld65 -o ENTROPY entropy.o -C ../linker_scripts/apple2_c00.inc
@@ -14,5 +15,8 @@ ENTROPY:	entropy.o
 entropy.o:	entropy.s
 	ca65 -o entropy.o entropy.s -l entropy.lst
 
+ENTROPY.BAS:	entropy.bas
+	$(TOKENIZE) < entropy.bas > ENTROPY.BAS
+
 clean:	
 	rm -f *~ *.o *.lst ENTROPY
diff --git a/two-liners/entropy.bas b/two-liners/entropy.bas
new file mode 100644
index 00000000..c95cd5c3
--- /dev/null
+++ b/two-liners/entropy.bas
@@ -0,0 +1,7 @@
+' Entropy
+' by Dave McKellar of Toronto
+' Two-line BASIC program
+' From Beagle Brother's Apple Mechanic Disk
+
+1  ROT=0:FOR I=1 TO 15:READ A,B:POKE A,B:NEXT:DATA 232,252,233,29,7676,1,7678,4,7679,0,7680,18,7681,63,7682,36,7683,36,7684,45,7685,45,7686,54,7687,54,7688,63,7689,0
+2  FOR I=1 TO 99:HGR2:FOR E=.08 TO .15 STEP .01:FOR Y=4 TO 189 STEP 6:FOR X=4 TO 278 STEP 6:SCALE=(RND(1)< E)*RND(1)*E*20+1:XDRAW 1 AT X,Y:NEXT:NEXT:NEXT:NEXT
diff --git a/two-liners/entropy.s b/two-liners/entropy.s
index b351a4fd..2c3936ba 100644
--- a/two-liners/entropy.s
+++ b/two-liners/entropy.s
@@ -13,26 +13,62 @@
 ;	SCALE=(RND(1)<E)*RND(1)*E*20+1: XDRAW 1 AT X,Y:
 ;	NEXT: NEXT: NEXT
 
+;BLT=BCC, BGE=BCS
 
 ; zero page locations
 HGR_SHAPE	=	$1A
+TEMP1_EXP	=	$93
+TEMP1_HO	=	$94
+TEMP1_MOH	=	$95
+TEMP1_MO	=	$96
+TEMP1_LO	=	$97
+FAC_EXP		=	$9D
+FAC_HO		=	$9E
+FAC_MOH		=	$9F
+FAC_MO		=	$A0
+FAC_LO		=	$A1
+FAC_SGN		=	$A2
+RND_EXP		=	$C9
+RND_HO		=	$CA
+RND_MOH		=	$CB
+RND_MO		=	$CC
+RND_LO		=	$CD
+RND_SGN		=	$CE
+
 HGR_SCALE	=	$E7
 HGR_ROTATION	=	$F9
+EPOS		=	$FC
 XPOS		=	$FD
 XPOSH		=	$FE
 YPOS		=	$FF
 
 ; ROM calls
+SNGFLT		=	$E301
+CONINT		=	$E6FB
+FMULT		=	$E97F
+RND		=	$EFAE
 HGR2		=	$F3D8
 HPOSN		=	$F411
 XDRAW0		=	$F65D
+; ROM constants
+TEN		=	$EA50
 
 entropy:
 
 loop:
 	jsr	HGR2			; HGR2
 
+	lda	#8
+	sta	EPOS
+
 eloop:	; FOR E=.08 TO .15 STEP .01:
+	; .08 .09 .10 .11 .12 .13 .14
+	; 0   1   2    3   4   5   6
+	; EINT 8   9  10   11  12   13  14
+	; E*20 160 180 200 220 240 260 280
+	; E*16 $80 $90 $A0 $B0 $C0 $D0 $E0
+	;      128 144 160 176 192 208 224
+	;      1.6 1.8 2.0 2.2 2.4 2.6 2.8
 
 	lda	#4
 	sta	YPOS
@@ -43,15 +79,52 @@ yloop:					; FOR Y=4 to 189 STEP 6
 	sta	XPOSH
 xloop:					; FOR X=4 to 278 STEP 6
 
-	lda	#1
-	sta	HGR_SCALE
 
 	; SCALE=(RND(1)<E)*RND(1)*E*20+1
+	;
+	; Equivalent to IF RND(1)<E THEN SCALE=RND(1)*E*20+1
+	;		ELSE SCALE=1
+
 	; E=.08 80% of time less, so 0 + (0 to .08)*20 = 0 to 1.6
 	; 80% of time 1 to 2.6, 20% of time 2 to 3.6
 	; E=.15 65% 0+(0 to .15)*20 = 0 to 3
 	; 65% 1 to 4, 45% 2 to 5
- 
+
+	; Note the Apple II generates a seed based on keypresses
+	; but by default RND is never seeded from there.
+	; Someone actually wrote an entire academic paper complaining about
+	; this
+	;
+	; J.W. Aldridge.  "Cautions regarding random number generation
+	;	on the Apple II", Behavior Research Methods, Instruments,
+	;	& Computers, 1987, 19 (4), 397-399.
+
+
+	jsr	RND			; put random value in FAC
+ 	; Compare to E
+
+	ldy	#>TEN
+	lda	#<TEN
+	jsr	FMULT
+
+	ldy	#>TEN
+	lda	#<TEN
+	jsr	FMULT
+
+	jsr	CONINT
+
+	; X is now RND(1)*100
+
+	cpx	EPOS
+	bcs	more
+less:
+	lda	#1
+	jmp	done
+more:
+	lda	#2
+done:
+	sta	HGR_SCALE
+
 
 
 	ldy	XPOSH
@@ -90,6 +163,17 @@ nexty:
 	cmp	#189
 	bcc	yloop
 ; NEXT E
+;	clc
+;	lda	EPOS
+;	adc	#16
+;	sta	EPOS
+;	cmp	#240
+
+
+	inc	EPOS
+	lda	EPOS
+	cmp	#15
+	bcc	eloop
 
 	jmp	loop