Thanks. Do I therefore able to conclude that none of the reductions using instance declarations are not performed because of potential overlapping instances?
william
From: Bulat Ziganshin <[EMAIL PROTECTED]> Reply-To: Bulat Ziganshin <[EMAIL PROTECTED]> To: "william kim" <[EMAIL PROTECTED]> CC: [email protected] Subject: Re: [Haskell-cafe] Principal type in Haskell Date: Thu, 22 Jun 2006 14:28:14 +0400 Hello william, Thursday, June 22, 2006, 1:22:32 PM, you wrote: > GHCi yields type f :: (Eq [a]) => a -> a -> Bool. > But according to the paper "Type classes: an exploration of the design > space", predicate Eq [a] should be reduced to Eq a. Is this reduction > performed here? What should be the principal type of f? Ghc, unlike H98, supports instances like this: instance Eq [MyType] where a==b = True so this extension to type inference allows to use such instance even if MyType is not in Eq class -- Best regards, Bulat mailto:[EMAIL PROTECTED]
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