[Haskell-beginners] Problem with typeclass

Stephen Tetley stephen.tetley at gmail.com
Sun Jun 20 06:03:02 EDT 2010

Hello Sebastien


> (fromJValue (JBool True)) :: Bool


> (fromJValue (JBool True)) :: JValue

The class function /fromJValue/ is polymorphic on its answer, so you
need to tell GHC / GHCi what type the answer will be. GHC can't infer
it because it could be more than one type.

Best wishes


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