Re: [Haskell-cafe] ANNOUNCE: vector-bytestring-0.0.0.0

On 16 October 2011 08:51, Stephen Tetley wrote:

On 15 October 2011 23:56, Bas van Dijk wrote:

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On 15 October 2011 23:17, Ertugrul Soeylemez wrote:

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Both instances are valid here, and there is no mechanism to choose one of them.

There is: OverlappingInstances[1] chooses the most specific instance. So in case someVector :: Vector Word8 the instance Show (Vector Word8) is chosen because it's the most specific.

This has the problem of incoherence in multi-module programs - GHC might chose different instances for the same type depending on compilation order. For a Show instance, this may be acceptable.

But is this a problem when both instances are exported from the same module and OverlappingInstances is only enabled in that module, as is the case here?