[Haskell-cafe] Problem with overlapping class instances

[Keean Schupke]

The trick here is to use a type to represent the constraint rather
than a class, if possible.

    Keean

Ralf Laemmel wrote:

> Instance selection and thereby overlapping resolution
> is *independent* of constraints. It is defined to be purely
> syntactical in terms of instance heads. See the HList paper
> for some weird examples.
>
> Ralf
>
>
> Graham Klyne wrote:
>
>>
>> The reported overlapping instance is [Char], which I take to be 
>> derived from the type constructor [] applied to type Char, this 
>> yielding a form that matches (cw c).  But the instance ConceptExpr 
>> (cw c) is declared to be dependent on the context ConceptWrapper cw 
>> c, which has *not* been declared for the type constructor [].
>>
>> GHCi with -fglasgow-exts is no more informative.
>>
>> What am I missing here?
>
>
>
>
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