PROGRAM macrame     !1986 april GWBasic to TRUE BASIC 2004 march
! © W.van Duyn 2004
SET MODE "color"
SET WINDOW 0,1199,0,903 !Aspect ratio 1:1 tuned to 1280x1024 res
SET BACKGROUND COLOR "white"
PRINT "Input Magnification mag (try: 1 to start)"
INPUT mag
PRINT "Input position dx, dy (try: 600,452 to start)"
INPUT dx,dy
PRINT "Input a,b,c (start: 79,30,80)"
INPUT a,b,c
CLEAR
LET x=1
LET y=1
FOR i = 1 to 1150000
LET xx=y-SGN(x)*SQR(ABS(b*x-c))
LET yy=a-x
LET x=xx
LET y=yy
LET xr=x*COS(.7854)+y*SIN(.7854)     !rotate axes 45degrees
LET yr=y*COS(.7854)-x*SIN(.7854)
LET j = mag*xr+dx
LET k = mag*yr+dy
    CALL colpatA(i)
PLOT j,k
NEXT i
END

SUB colpatA(i)
IF i<150000 THEN SET COLOR 9      !"blue"
IF i>150000 AND i<300000 THEN SET COLOR 12     !"red"
IF i>300000 AND i<500000 THEN SET COLOR 14     !"yellow"
IF i>500000 AND i<800000 THEN SET COLOR 10     !"green"
IF i>800000 AND i<950000 THEN SET COLOR 13     !"magenta"
IF i>950000 THEN SET COLOR 11     !"cyan"
END SUB