Error tuple: Non type-variable argument in the constraint: Integral (a, a)

Question

I have seen an example where you define the tuple type in this way:

countRepetitions :: (Integral a, Integral (a,a)) => [a] -> a -> (a,a)

But when I execute the code appears the message: Non type-variable argument in the constraint: Integral (a, a) How can I declare a tuple type?

Answer 1

You don't need to constraint with Integral (a, a). The constraint Integral a forces all values for type a to be Integral. Try rewriting it like this:

countRepetitions :: Integral a => [a] -> a -> (a,a)