Re: [Haskell-cafe] ($) not as transparent as it seems

catamorphism:

On Thu, Feb 3, 2011 at 12:44 PM, Steffen Schuldenzucker wrote:

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Dear cafe,

does anyone have an explanation for this?:

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error (error "foo") *** Exception: foo

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error $ error "foo" *** Exception: *** Exception: foo

Have you read the intermediate Core (using -ddump-simpl) for each variation?

A. GHC.Base.bindIO @ GHC.Prim.Any @ [()] ((GHC.Err.error @ [GHC.Types.Char] (GHC.Base.unpackCString# "foo")) `cast` (CoUnsafe [GHC.Types.Char] (GHC.Types.IO GHC.Prim.Any) :: [GHC.Types.Char] ~ GHC.Types.IO GHC.Prim.Any)) ((\ (it_ade :: GHC.Prim.Any) (eta_B1 :: GHC.Prim.State# GHC.Prim.RealWorld) -> ((GHC.Base.returnIO @ [()] (GHC.Types.: @ () (it_ade `cast` (CoUnsafe GHC.Prim.Any () :: GHC.Prim.Any ~ ())) (GHC.Types.[] @ ()))) `cast` (GHC.Types.NTCo:IO [()] :: GHC.Types.IO [()] ~ (GHC.Prim.State# GHC.Prim.RealWorld -> (# GHC.Prim.State# GHC.Prim.RealWorld, [()] #)))) eta_B1) `cast` (GHC.Prim.Any -> sym (GHC.Types.NTCo:IO [()]) :: (GHC.Prim.Any -> GHC.Prim.State# GHC.Prim.RealWorld -> (# GHC.Prim.State# GHC.Prim.RealWorld, [()] #)) ~ (GHC.Prim.Any -> GHC.Types.IO [()]))) B. GHC.Base.bindIO @ GHC.Prim.Any @ [()] (GHC.Base.$ @ [GHC.Types.Char] @ (GHC.Types.IO GHC.Prim.Any) (GHC.Err.error @ (GHC.Types.IO GHC.Prim.Any)) (GHC.Err.error @ [GHC.Types.Char] (GHC.Base.unpackCString# "foo"))) ((\ (it_aib :: GHC.Prim.Any) (eta_B1 :: GHC.Prim.State# GHC.Prim.RealWorld) -> ((GHC.Base.returnIO @ [()] (GHC.Types.: @ () (it_aib `cast` (CoUnsafe GHC.Prim.Any () :: GHC.Prim.Any ~ ())) (GHC.Types.[] @ ()))) `cast` (GHC.Types.NTCo:IO [()] :: GHC.Types.IO [()] ~ (GHC.Prim.State# GHC.Prim.RealWorld -> (# GHC.Prim.State# GHC.Prim.RealWorld, [()] #)))) eta_B1) `cast` (GHC.Prim.Any -> sym (GHC.Types.NTCo:IO [()]) :: (GHC.Prim.Any -> GHC.Prim.State# GHC.Prim.RealWorld -> (# GHC.Prim.State# GHC.Prim.RealWorld, [()] #)) ~ (GHC.Prim.Any -> GHC.Types.IO [()])))