PROGRAM Peano_Gosper_Curve_13_Triple   !(© W.van Duyn 21st April 2004)
SET MODE "color"
SET WINDOW 0,1199,0,903
SET BACKGROUND COLOR "white"
CLEAR
CALL init
END

SUB init
OPTION ANGLE degrees
PRINT "input: x try 400, y try 400"
INPUT x,y
PRINT "input: Side try 160, level try 3, dimension 6"
INPUT side,level,ak
CLEAR
SET COLOR "black"
FLOOD 1,1
LET a=0
LET k=360/ak
LET r=2+2*COS(k)
LET lev=level
FOR i = 1 TO ak/2
SET COLOR (3*i+6)
CALL shift(side,level,a,x,y,k,r)
NEXT i
END SUB

SUB shift(side,level,a,x,y,k,r)
LET lev=level
LET d=side/(r^(level))
CALL move1(d,lev,a,x,y,k)
CALL turnRIGHT(a,k)
CALL turnRIGHT(a,k)
END SUB

SUB move1(d,lev,a,x,y,k)
IF lev=0 THEN
CALL travelON(d,a,x,y)
EXIT IF
ELSE
CALL move2(d,lev-1,a,x,y,k)!1
CALL turnRIGHT(a,k)
CALL move1(d,lev-1,a,x,y,k)!2
CALL turnRIGHT(a,k)
CALL turnRIGHT(a,k)
CALL move1(d,lev-1,a,x,y,k)!3
CALL turnLEFT(a,k)
CALL move2(d,lev-1,a,x,y,k)!4
CALL turnLEFT(a,k)
CALL turnLEFT(a,k)
CALL move2(d,lev-1,a,x,y,k)!5
CALL turnRIGHT(a,k)
CALL move1(d,lev-1,a,x,y,k)!6
CALL move1(d,lev-1,a,x,y,k)!7
CALL turnRIGHT(a,k)
CALL turnRIGHT(a,k)
CALL move1(d,lev-1,a,x,y,k)!8
CALL turnRIGHT(a,k)
CALL move2(d,lev-1,a,x,y,k)!9
CALL turnLEFT(a,k)
CALL move1(d,lev-1,a,x,y,k)!10
CALL turnRIGHT(a,k)
CALL move2(d,lev-1,a,x,y,k)!11
CALL turnLEFT(a,k)
CALL turnLEFT(a,k)
CALL move2(d,lev-1,a,x,y,k)!12
CALL turnLEFT(a,k)
CALL move1(d,lev-1,a,x,y,k)!13
CALL turnLEFT(a,k)
END IF
END SUB

SUB move2(d,lev,a,x,y,k)
IF lev=0 THEN
CALL travelON(d,a,x,y)
EXIT IF
ELSE
CALL turnRIGHT(a,k)
CALL move2(d,lev-1,a,x,y,k)!13
CALL turnRIGHT(a,k)
CALL move1(d,lev-1,a,x,y,k)!12
CALL turnRIGHT(a,k)
CALL turnRIGHT(a,k)
CALL move1(d,lev-1,a,x,y,k)!11
CALL turnLEFT(a,k)
CALL move2(d,lev-1,a,x,y,k)!10
CALL turnRIGHT(a,k)
CALL move1(d,lev-1,a,x,y,k)!9
CALL turnLEFT(a,k)
CALL move2(d,lev-1,a,x,y,k)!8
CALL turnLEFT(a,k)
CALL turnLEFT(a,k)
CALL move2(d,lev-1,a,x,y,k)!7
CALL move2(d,lev-1,a,x,y,k)!6
CALL turnLEFT(a,k)
CALL move1(d,lev-1,a,x,y,k)!5
CALL turnRIGHT(a,k)
CALL turnRIGHT(a,k)
CALL move1(d,lev-1,a,x,y,k)!4
CALL turnRIGHT(a,k)
CALL move2(d,lev-1,a,x,y,k)!3
CALL turnLEFT(a,k)
CALL turnLEFT(a,k)
CALL move2(d,lev-1,a,x,y,k)!2
CALL turnLEFT(a,k)
CALL move1(d,lev-1,a,x,y,k)!1
END IF
END SUB

SUB travelON(d,a,x,y)
OPTION ANGLE degrees
LET x2=x+d*cos(a)
LET y2=y+d*sin(a)
PLOT x,y;x2,y2
LET x=x2
LET y=y2
END SUB

SUB turnLEFT(a,k)
LET a=a+k
END SUB

SUB turnRIGHT(a,k)
LET a=a-k
END SUB