Re: [Haskell-cafe] Type checking of partial programs

zunino:

ac wrote:

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foo :: [Foo] -> foo xs = map 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:

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: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