ntKey :: Amount -> MixedAmountKey
amountKey amt@Amount{acommodity=c} = case aprice amt of
    Nothing             -> MixedAmountKeyNoPrice    c
    Just (TotalPrice p) -> MixedAmountKeyTotalPrice c (acommodity p)
    Just (UnitPrice  p) -> MixedAmountKeyUnitPrice  c (acommodity p) (aquantity p)

-- | The empty mixed amount.
nul
amountKey :: Amount -> MixedAmountKey
amountKey amt@Amount{acommodity=c} = case aprice amt of
    Nothing             -> MixedAmountKeyNoPrice    c
    Just (TotalPrice p) -> MixedAmountKeyTotalPrice c (acommodity p)
    Just (UnitPrice  p) -> MixedAmountKeyUnitPrice  c (acommodity p) (aquantity p)

-- | The empty mixed amount.
amountKey amt@Amount{acommodity=c} = case aprice amt of
    Nothing             -> MixedAmountKeyNoPrice    c
    Just (TotalPrice p) -> MixedAmountKeyTotalPrice c (acommodity p)
    Just (UnitPrice  p) -> MixedAmountKeyUnitPrice  c (acommodity p) (aquantity p)

-- | The empty mixed amount.