-- | The top k customers from one given country (by number of orders)
topCustomers :: Integer -> Text -> Q [(Text, Decimal)]
topCustomers k n =
    [ pair (c_nameQ c) (c_acctbalQ c)
    | c <- topK k (length . custOrders)
                  [ c | c <- customers, c `custFromNation` n ]
    ]
topCustomers :: Integer -> Text -> Q [(Text, Decimal)]
topCustomers k n =
    [ pair (c_nameQ c) (c_acctbalQ c)
    | c <- topK k (length . custOrders)
                  [ c | c <- customers, c `custFromNation` n ]
    ]
topCustomers k n =
    [ pair (c_nameQ c) (c_acctbalQ c)
    | c <- topK k (length . custOrders)
                  [ c | c <- customers, c `custFromNation` n ]
    ]