instance visibility (was: Re: The base library and GHC 6.10)

Claus Reinke claus.reinke at talk21.com
Thu Sep 25 17:49:27 EDT 2008


>> I'd be interested to see a design that allows for local instances, in a
>> way that doesn't cause problems like in the URL above, but as far as I
>> know none exist yet.
>
> While this has come up now and then, most recently here
>
>    http://www.haskell.org/pipermail/haskell-prime/2008-May/002601.html
>    http://www.haskell.org/pipermail/libraries/2008-September/010623.html

of course, as soon as I hit send I recalled:

    Wolfram Kahl and Kahl Scheffczyk,
    Named Instances for Haskell Type Classes
    http://www.cs.uni-bonn.de/~ralf/hw2001/4.pdf

    Derek Dreyer, Robert Harper, and Manuel M. T. Chakravarty
    Modular Type Classes
    http://www.cse.unsw.edu.au/~chak/papers/DHC07.html

while searching for those urls, I also discovered that Paul replied
to the 2001 paper in a 1992 email:

    http://www.cse.unsw.edu.au/~dons/haskell-1990-2000/msg00727.html

That's what I call foresight!-)

Claus

Ps. there have also been encodings of named instances, iirc.





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