Say I've got a type "Month" declared as an instance of the "Enum" class, and a
type "MonthPair" declared as a pair of months:
data Month = January | February
| March | April
| May | June
| July | August |
September | October |
November | December
deriving (Eq, Enum, Ord, Show)
type MonthPair = (Month, Month) deriving
(Enum)
The "deriving" on "MonthPair" gives me the error "parse error on input
'deriving'".
Why is this error generated? Is there a syntax error, or is there a conceptual
problem with enumerating a Cartesian product, such as Month x Month? The
cardinality of the Cartesian product is finite (including the bottom values,
cardinality = 1 + (12 + 1)*(12 + 1) = 170), and so the product is amenable at
least to some arbitrary enumeration (such as Cantor's diagonal method).
Thanks.
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