21 Mar
2008
21 Mar
'08
4:38 a.m.
zunino:
ac wrote:
foo :: [Foo] -> <placeholder 1> foo xs = map <placeholder 2> xs
What are the possible type signatures for placeholder 1 and the possible expressions for placeholder 2?
A nice GHCi trick I learned from #haskell:
:t let foo xs = map ?placeholder2 xs in foo
forall a b. (?placeholder2::a -> b) => [a] -> [b]
Also, the djinn tool might provide some actual expression for placeholder 2.
Zun.
Yes, it turns out implicit parameters provide a great mechanism for doing type checker queries :) -- Don