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List:       haskell-cafe
Subject:    Re: [Haskell-cafe] Top Level etc.
From:       Keean Schupke <k.schupke () imperial ! ac ! uk>
Date:       2005-01-19 13:31:48
Message-ID: 41EE6144.6090308 () imperial ! ac ! uk
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I may have got this wrong, but I think you can do named instances 
without any extensions,
by using datatypes and fundeps:

data Instance0
data Instance1

instance0 :: Instance0
instance0 = undefined

instance1 :: Instance1
instance1 = undefined

class Named a b | a -> b
    test :: a -> b -> b
instance Named Instance0 Int
    test _ a = a + a
instance Named Instance1 Float
    test _ a = a * a


test instance0 1
test instance1 1.5


    Keean.

Benjamin Franksen wrote:

>You will probably find this paper interesting: Wolfram Kahl and Jan 
>Scheffczyk: "Named Instances for Haskell Type Classes", 
>http://www.informatik.uni-bonn.de/~ralf/hw2001/4.pdf
>  
>

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