Re: [Haskell-cafe] Confusing type specialisation in ghci

David Carter wrote:

This is all as I would expect so far, but:

Prelude> let sqlist = map sq Prelude> :t sqlist sqlist :: [Integer] -> [Integer]

And indeed, I get

Prelude> sqlist [2.5]

<interactive>:1:8: No instance for (Fractional Integer) ... etc

The dreaded Monomorphism Restriction, which GHCi chooses to apply after every line you input. You could say "let sqlist a = map sq a" (syntactically having arguments makes the defaulting of (Num a => [a] -> [a]) not apply), or just use `ghci -fno-monomorphism-restriction`. Isaac