PROGRAM SIERPINSKI_Cross_motif_carpets   !© W.van Duyn 7th MAY 2004
SET MODE "color"
SET WINDOW 0,1199,0,903
SET COLOR 16
BOX AREA 0,1199,0,903
FLOOD 1,1
SET BACKGROUND COLOR "black"
SET COLOR "white"
PRINT "select carpet - Sierpinski,gold,median,square,thin,curio 1,2,3,4,5 or 6"
INPUT s
CLEAR
PRINT" cross motif carpets I.F.S."
PRINT" © W.VanDuyn 2004"
LET x=1
LET y=1
LET a=0
LET f=600
IF s=1 OR s >6 THEN
LET p=1/3
LET q=p
PRINT " Sierpinski Carpet"
END IF
IF s=2 THEN
REM LET fi= 0.618034
LET p= 0.381966
LET q= 0.236068
PRINT " Golden Ratio Cross Carpet"
END IF
IF s=3 THEN
LET p=0.4
LET q=p/2
PRINT " Median Ratio Cross Carpet"
END IF
IF s=4 THEN
LET p=SQR(2)-1
LET q=3-2*SQR(2)
PRINT " Square Root of Two Cross Carpet?"
END IF
IF s=5 THEN
LET p=0.4538
LET q=0.0924
PRINT " Thin Ratio Cross Carpet"
END IF
IF s=6 THEN
LET p=0.3333333
LET q=-0.33333333
PRINT " T Square Curio Carpet"
END IF
RANDOMIZE
FOR n= 1 TO 5000000
LET a = INT(RND*8)+1
IF a =1 THEN
LET x1=p*x
LET y1=p*y
END IF
IF a=2 THEN
LET x1=q*x+0
LET y1=q*y+p
END IF
IF a=3 THEN
LET x1=p*x+0
LET y1=p*y+(p+q)
END IF
IF a=4 THEN
LET x1=q*x+p
LET y1=q*y+2*p
END IF
IF a =5 THEN
LET x1=p*x+(p+q)
LET y1=p*y+(p+q)
END IF
IF a=6 THEN
LET x1=q*x+2*p
LET y1=q*y+p
END IF
IF a=7 THEN
LET x1=p*x+(p+q)
LET y1=p*y
END IF
IF a=8 THEN
LET x1=q*x+p
LET y1=q*y
END IF
SET COLOR MIX (a+100) 1,1-a/8,a/8
SET COLOR MIX (a+200) a/8,1,1-a/8
SET COLOR MIX (a+300) 1-a/8,a/8,1
IF mod(a,3) = 0 THEN SET COLOR a+100
IF mod(a,3) = 1 THEN SET COLOR a+200
IF mod(a,3) = 2 THEN SET COLOR a+300
LET x=x1
LET y=y1
IF n>10 THEN PLOT 600+f*x-f/2,450+f*y-f/2
NEXT n
END