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,
?b::t1,
?a::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
second argument?
I'm curios as to how the example you give actually works - I don't
recognise that syntax at all...
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