On Dec 21, 2007 4:39 AM, Ronald Guida
Finally, I tried to define vecLength, but I am getting an error.
vecLength :: (Peano s) => Vec s t -> Int vecLength _ = pToInt (pGetValue :: s)
The s in (pGetValue :: s) is different from the s in (Peano s). Use the "scoped type variables" extension: vecLength :: forall s. (Peano s) => Vec s t -> Int vecLength _ = pToInt (pGetValue :: s) The forall introduces a scope for s, which type signatures usually do not. Luke
< Could not deduce (Peano s1) from the context () < arising from a use of `pGetValue' < Possible fix: < add (Peano s1) to the context of the polymorphic type `forall s. s' < In the first argument of `pToInt', namely `(pGetValue :: s)' < In the expression: pToInt (pGetValue :: s) < In the definition of `vecLength': < vecLength _ = pToInt (pGetValue :: s)
Any suggestions? -- Ron
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