You can use
to get information about a data type. There, you can also see that
Bool belongs to the
Enum type classes. Hence, you can get all elements of the data type using
[minBound ..] :: [ Bool]
Then, you can get the cardinality using
length ([minBound ..] :: [Bool]). There may be easier ways to get the cardinality of a bounded, enumerated data type.
In any case, and judging from your other questions, I advice you to read an introductiory book about Haskell. See here: Documentation.