[Haskell-cafe] hiding instance definitions in imported modules or
redefining them, can it be done?
jvlask at hotmail.com
Fri Jul 3 04:13:42 EDT 2009
Is there a way to hide instance definitions when importing a module for
I want to import Data.Monoid but wish to redefine the instance of Monoid for
I don't suppose this is possible?
Specifically, I wish to define a specialised instance of Monoid for
String->Int, but it seems overlapping instances will not give me what I
want, as this option seems to need to be applied at the definition site (aka
Data.Monoid module, looking for confirmation of this?).
The easy fix is just to do newtype M a b = M (a->b) etc..., but I was
hopping to avoid this. I've encountered this issue several times. Why can't
we redefine instances? I can't of thought that there are any seriouse
technical issues in doing so? If so what are they?
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