Function unit_fraction(o.x, o.y, u.x, u.y, v.x, v.y, nu, nv):
    du.x = u.x / (nu-1)
    du.y = u.y / (nu-1)
    dv.x = u.x / (nv-1)
    dv.y = u.y / (nv-1)
    p.x = o.x
    p.y = o.y
    h = 0
    For i = 1..nv:
       c.x = p.x
       c.y = p.y
       For j = 1..nu:
           If (c.x >= 0) And (c.x <= 1) And
              (c.y >= 0) And (c.y <= 1):
               h = h + 1
           End If
       End For
       c.x = c.x + dv.x
       c.y = c.y + dv.y
    End For
    Return h / (nu * nv)
End Function