/*
 *	PLOTTING DEMO PROGRAMS.  PLOT SUPERIMPOSED SERPINSKI
 *	CURVES OF ORDER 1 .. N.  PROGRAM ADAPTED FREELY FROM
 *	"ALGORITHMS + DATA STRUCTURES = PROGRAMS",
 *	  NIKLUAS WIRTH, PRENTICE-HALL INC., 
 *	  ENGLEWODD CLIFFS, NEW JERSEY
 *
 *	ADAPTATION BY ANDREW LEUBKER, CARLETON COLLEGE,
 *	NORTHFIELD, MN. 55057.
 */

/*PLOP SIERPINSKI CURVES OF ORDERS 1 TO N*/
CONST  OFF=100; H0=512;
VAR  I,H,N,X,Y,X0,Y0,OLDX,OLDY: INTEGER;
PROCEDURE SETPLOP;
BEGIN
  MOVE(X+OFF,Y+OFF)
END;
PROCEDURE PLOP;
BEGIN
  DRAW(X+OFF,Y+OFF);
  OLDX:=X; OLDY:=Y
END;
PROCEDURE STARPLOP;
BEGIN
  INITPLOT;
  MOVE(0,0)
END;
PROCEDURE A(I: INTEGER); FORWARD;
PROCEDURE B(I:INTEGER); FORWARD;
PROCEDURE C(I:INTEGER); FORWARD;
PROCEDURE D(I:INTEGER); FORWARD;
PROCEDURE A;
BEGIN IF I>0 THEN
     begin a(I-1); x:=x+h; y:=y-h; PLOP;
	B(I-1); X:=X+2*H; PLOP;
	D(I-1); X:=X+H; Y:=Y+H; PLOP;
	A(I-1)
      END
END;
PROCEDURE B;
BEGIN IF I>0 THEN
     BEGIN B(I-1); X:=X-H; Y:=Y-H; PLOP;
	C(I-1); Y:=Y-2*H; PLOP;
	A(I-1); X:=X+H; Y:=Y-H; PLOP;
	B(I-1)
     END
END;
PROCEDURE C;
BEGIN IF I>0 THEN
     BEGIN C(I-1); X:=X-H; Y:=Y+H; PLOP;
	D(I-1); X:=X-2*H; PLOP;
	B(I-1); X:=X-H; Y:=Y-H; PLOP;
	C(I-1)
     END
END;
PROCEDURE D;
BEGIN IF I>0 THEN
     BEGIN D(I-1); X:=X+H; Y:=Y+H; PLOP;
	A(I-1); Y:=Y+2*H; PLOP;
	C(I-1); X:=X-H; Y:=Y+H; PLOP;
	D(I-1)
     END
END;
BEGIN REWRITE(OUTPUT,'TT:');
  STARPLOP;
  REPEAT
    WRITE('LEVELS? ');
    READLN(N);
    IF N<1 THEN WRITE('MUST BE MORE THAN 0... ')
  UNTIL N>0;
  ERASE;
  I:=0; H:=H0 DIV 4; X0:=2*H; Y0:=3*H;
  REPEAT I:=I+1; X0:=X0-H;
    H:=H DIV 2; Y0:=Y0+H;
    X:=X0; Y:=Y0; SETPLOP;
    A(I); X:=X+H; Y:=Y-H; PLOP;
    B(I); X:=X-H; Y:=Y-H; PLOP;
    C(I); X:=X-H; Y:=Y+H; PLOP;
    D(I); X:=X+H; Y:=Y+H; PLOP;
  UNTIL I=N;
  ENDPLOT
END.