[Haskell-cafe] Hoogle? [Stacking monads]
andrewcoppin at btinternet.com
Wed Oct 8 15:11:05 EDT 2008
Ryan Ingram wrote:
> There is such a tool, it's called ghci :)
> It just takes a bit of massaging to do what you want:
> ghci> :set -fglasgow-exts
> ghci> :t (?f some_func [?a .. ?b])
> Here's an example:
> Prelude> :t ?f map [?a .. ?b]
> ?f map [?a .. ?b] :: forall t a b t1.
> (Enum t1,
> ?f::((a -> b) -> [a] -> [b]) -> [t1] -> t)
> => t
> This tells you the types the variables have to have, and the type of
> the expression.
> Judicious use of (undefined :: type_signature) can also help.
Using undefined is already a standard technique for me. But what it
doesn't let you do is
foo (undefined :: Bar x) (undefined) :: Bar y -- What type is the
I'm curios as to how the example you give actually works - I don't
recognise that syntax at all...
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