Benjamin Franksen wrote:
I still have problems. They are probably due to a wrong definition of the operator (#). Note that (#) is nowhere defined inside the HList sources, so I assumed an inverse application aoperator. This is my program now:
No, # is the record selection operator from the HList based records. infixr 9 # m # field = m .!. field Keean.
On Monday 29 November 2004 21:47, Keean Schupke wrote:
Benjamin Franksen wrote:
I still have problems. They are probably due to a wrong definition of the operator (#). Note that (#) is nowhere defined inside the HList sources, so I assumed an inverse application operator. This is my program now:
No, # is the record selection operator from the HList based records.
infixr 9 # m # field = m .!. field
Of course, stupid me. Ok, I changed that. Still won't compile. I post only the first of four type errors (they are all about 40 lines long; note that the inferred type below is almost longer than the complete test program). TestObject.hs:16: No instances for (HFind' b4 (Proxy GetX) (HCons (Proxy GetX) (HCons (Proxy MoveD) HNil)) n1, HEq (Proxy GetX) (Proxy MutableX) b4, HFind' b3 (Proxy MoveD) (HCons (Proxy GetX) (HCons (Proxy MoveD) HNil)) n, HEq (Proxy MoveD) (Proxy MutableX) b3, HLookupByHNat n (HCons (IORef a) (HCons (IO a) (HCons (a -> IO ()) HNil))) (a1 -> IO t), HLookupByHNat n1 (HCons (IORef a) (HCons (IO a) (HCons (a -> IO ()) HNil))) (IO a2), HOr b2 HFalse HFalse, HEq (Proxy GetX) (Proxy MoveD) b2, HOr b b' HFalse, HOr b1 HFalse b', HEq (Proxy MutableX) (Proxy MoveD) b1, HEq (Proxy MutableX) (Proxy GetX) b) arising from use of `.*.' at TestObject.hs:16 In the second argument of `($)', namely `(mutableX .=. x) .*. ((getX .=. (readIORef x)) .*. ((moveD .=. (\ d -> modifyIORef x ((+) d))) .*. emptyRecord))' In the result of a 'do' expression: returnIO $ ((mutableX .=. x) .*. ((getX .=. (readIORef x)) .*. ((moveD .=. (\ d -> modifyIORef x ((+) d))) .*. emptyRecord))) In the definition of `point': point = do x <- newIORef 0 returnIO $ ((mutableX .=. x) .*. ((getX .=. (readIORef x)) .*. ((moveD .=. (\ d -> modifyIORef x ((+) d))) .*. emptyRecord))) Ben
Benjamin Franksen wrote:
Of course, stupid me. Ok, I changed that. Still won't compile. I post only the
first of four type errors (they are all about 40 lines long; note that the inferred type below is almost longer than the complete test program).
You'd probably need this as well: {-# OPTIONS -fglasgow-exts #-} {-# OPTIONS -fallow-undecidable-instances #-} {-# OPTIONS -fallow-overlapping-instances #-} and: module SimpleOO where import CommonMain hiding (HDeleteMany, hDeleteMany, TypeCast,typeCast) import GhcSyntax import GhcExperiments import TypeEqBoolGeneric import TypeEqGeneric1 import TypeCastGeneric1 import Label4 import Data.Typeable -- needed for showing labels import Data.IORef import GHC.IOBase The source code for this and more examples is downloadable from: http://www.cwi.nl/~ralf/OOHaskell, The import list is quite long as this using the HList library from the paper, which has different definitions of TypeEq available etc... Overlapping instances are not required for all definitions of type equality, just the generic ones. Keean.
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Benjamin Franksen -
Keean Schupke