elipsev2

-- drawElipse <semi_major_axis> <semi_minor_axis>
-- place turtle facing semi-minor axis in the center
args = {...}
sMa = args[1]
sma = args[2]

print(sMa)
print(sma)

stage = 1
running = true
selectedItem = 1

--[[stages 1=started, moving toward sma
           2=moving right, back
           3=moving left, back
           4=moving left, forward
           5=moving right, forward]]--

location = {x=0, y=0}
foci = {{x=0, y=0},{x=0,y=0}}

function findFoci()
    dF = math.sqrt((sMa*sMa)-(sma*sma))
    foci[1].x = math.floor(dF)
    foci[2].x = -(math.floor(dF))
end

function move(dir)
-- dir = 1 forward, 2 = forward/right, 3 = right, 4 = back/right, 5 = back, 6 = back/left, 7 = left, 8 = forward/left
-- note: turtle will ALWAYS face the same direction
    if dir == 1 then
        if turtle.forward() then
          location.y = location.y + 1
        end
    elseif dir == 2 then
        move(1)
        move(3)
    elseif dir == 3 then
      turtle.turnRight()
      if turtle.forward() then
        location.x = location.x + 1
      end
      turtle.turnLeft()
    elseif dir == 4 then
        move(5)
        move(3)
    elseif dir == 5 then
        if turtle.back() then
            location.y = location.y - 1
        end
    elseif dir == 6 then
        move(5)
        move(7)

    elseif dir == 7 then
        turtle.turnLeft()
            if turtle.forward() then
                location.x = location.x - 1
            end
        turtle.turnRight()
    elseif dir == 8 then
        move(1)
        move(7)
    end

end

function focalDistance(pos)
  dx1 = pos.x - foci[1].x
  dx2 = pos.x - foci[2].x
  dy1 = pos.y - foci[1].y
  dy2 = pos.y - foci[2].y

  print("Foci:"..textutils.serialize(foci))
  print("Pos:"..textutils.serialize(pos))

  df1 = math.sqrt(dx1*dx1 + dy1*dy1)
  df2 = math.sqrt(dx2*dx2 + dy2*dy2)

  return math.floor(df1+df2)
end

function chooseItem()
  if turtle.getItemCount(selectedItem) < 2 then
    selectedItem = selectedItem + 1
  end
  turtle.select(selectedItem)
end

function main()
    chooseItem()
    pos = {}
    print("Stage: "..tostring(stage))
    if stage == 1 then
        move(1)
        print("location: " ..textutils.serialize(location))
        print("Focal Dist: "..tostring(math.floor(focalDistance(location))))
        print("Major Axis: "..tostring(tonumber(sMa)*2))
        if math.floor(focalDistance(location)) == tonumber(sMa)*2 then
            turtle.placeUp()
            stage = 2
            return
        end
    elseif stage == 2 then
        pos.x = location.x + 1
        pos.y = location.y
        if math.floor(focalDistance(pos)) == tonumber(sMa)*2 then
            dir = 3
        else
            pos.x = location.x + 1
            pos.y = location.y - 1
            if math.floor(focalDistance(pos)) == tonumber(sMa)*2 then
                dir = 4
            else
                pos.x = location.x
                pos.y = location.y - 1
                if math.floor(focalDistance(pos)) == tonumber(sMa)*2 then
                    dir = 5
                end
            end
        end
        move(dir)
        turtle.placeUp()
        if location.y == 0 then
            stage = 3
            return
        end

    elseif stage == 3 then
        pos.x = location.x
        pos.y = location.y - 1
        if math.floor(focalDistance(pos)) == tonumber(sMa)*2 then
            dir = 5
        else
            pos.x = location.x - 1
            pos.y = location.y - 1
            if math.floor(focalDistance(pos)) == tonumber(sMa)*2 then
                dir = 6
            else
                pos.x = location.x - 1
                pos.y = location.y
                if math.floor(focalDistance(pos)) == tonumber(sMa)*2 then
                    dir = 7
                end
            end
        end
        move(dir)
        turtle.placeUp()
        if location.x == 0 then
            stage = 4
            return
        end

    elseif stage == 4 then
        pos.x = location.x - 1
        pos.y = location.y
        if math.floor(focalDistance(pos)) == tonumber(sMa)*2 then
            dir = 7
        else
            pos.x = location.x - 1
            pos.y = location.y + 1
            if math.floor(focalDistance(pos)) == tonumber(sMa)*2 then
                dir = 8
            else
                pos.x = location.x
                pos.y = location.y + 1
                if math.floor(focalDistance(pos)) == tonumber(sMa)*2 then
                    dir = 1
                end
            end
        end
        move(dir)
        turtle.placeUp()
        if location.y == 0 then
            stage = 5
            return
        end
    elseif stage == 5 then
        pos.x = location.x
        pos.y = location.y + 1
        if math.floor(focalDistance(pos)) == tonumber(sMa)*2 then
            dir = 1
        else
            pos.x = location.x + 1
            pos.y = location.y + 1
            if math.floor(focalDistance(pos)) == tonumber(sMa)*2 then
                dir = 2
            else
                pos.x = location.x + 1
                pos.y = location.y
                if math.floor(focalDistance(pos)) == tonumber(sMa)*2 then
                    dir = 3
                end
            end
        end
        move(dir)
        turtle.placeUp()
        if location.x == 0 then
            stage = 6
            return
        end

    elseif stage == 6 then
        move(5)
        if location.x == 0 and location.y == 0 then
            running = false
        end
    end
end

findFoci()
while running do
  parallel.waitForAny(main)
end