move.lua

function h2xy(h)
    if h == 0 then
        return 0,1
    elseif h == 1 then
        return 1,0
    elseif h == 2 then
        return 0,-1
    elseif h == 3 then
        return -1,0
    end
    return 0,0

end

function from_to_heading (ch,th)
    if(ch==th) then
        return 0
    end
   if(math.abs(ch-th)==2) then
        turtle.turnLeft()
        turtle.turnLeft()
    elseif (ch-th == -1 or ch-th == 3) then
        turtle.turnRight()
    else
        turtle.turnLeft()
    end

end

function move_towards (cx,cy,cheading,tx,ty )
    moved = false
    if cx != tx then
        if (cx>tx) then
            from_to_heading(cheading,3)
            cheading = 3
            moved = turtle.forward()
        elseif (cx<tx) then
            from_to_heading(cheading,1)
            cheading = 1
            moved = turtle.forward()
        end
    elseif (cy != ty) then
        if(cy>ty) then
            from_to_heading(cheading,2)
            cheading = 2
            moved = turtle.forward()
        elseif (cy<ty) then
            from_to_heading(cheading,0)
            cheading = 0
            moved = turtle.forward()
        end
    end
    dx,dy = h2xy(cheading)
    if(moved) then
        cx = cx+dx
        cy = cy+dy
    end
    return moved,cheading,cx,cy
end


function move_from_to(cx,cy,cheading,tx,ty)
    while cx!= tx or cy != ty do
        moved,nheading, nx,ny = move_towards(cx,cy,cheading,tx,ty)
        cx = nx
        cy = ny
        cheading = nheading
    end
end