PROGRAM simple_map
! corrected on 1/30/97
CALL initial(x,y)
FOR i = 1 to 100000
    LET xnew = 1 - y + abs(x)
    LET y = x
    LET x = xnew
    PLOT x,y
NEXT i
END

SUB initial(x0,y0)
    INPUT prompt "initial value of x = ": x0
    INPUT prompt "initial value of y = ": y0
    CLEAR
    LET xmin = -3
    LET xmax = 8
    LET ymin = -3
    LET ymax = 8
    LET mx = 0.01*(xmax - xmin)   ! margin
    LET my = 0.01*(ymax - ymin)
    SET WINDOW xmin - mx,xmax + mx,ymin - my,ymax + my
    BOX LINES xmin,xmax,ymin,ymax      ! draw border
    ASK MAX COLOR mc
    IF mc > 2 then SET COLOR "blue"
END SUB