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tokiwoousaka/gist:4696909

Created February 2, 2013 11:11
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gistfile1.hs
module Main where
class C c where
class A a where
cFrom :: C b => a -> b
instance C c => A ((,) c a) where
cFrom x = fst x --ghc cant deduce c 2 b
@func-hs
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func-hs commented Mar 18, 2013

この書き方をどうにかしたいなら、MultiParamTypeClassesとTypeFamiliesを組み合わせるしかないような気がする

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