prop_setBoth :: Instance.Instance -> Types.Ndx -> Types.Ndx -> Bool
prop_setBoth inst pdx sdx =
  Instance.pNode si == pdx && Instance.sNode si == sdx
    where si = Instance.setBoth inst pdx sdx
prop_setBoth :: Instance.Instance -> Types.Ndx -> Types.Ndx -> Bool
prop_setBoth inst pdx sdx =
  Instance.pNode si == pdx && Instance.sNode si == sdx
    where si = Instance.setBoth inst pdx sdx
prop_setBoth inst pdx sdx =
  Instance.pNode si == pdx && Instance.sNode si == sdx
    where si = Instance.setBoth inst pdx sdx