multi-parametric type class

[Javier Torres Salgado]

Hi,

Nowadays I am using Hugs 98 interpreter (2001 version) to finish my final
work to get my Computer Master Degree at Instituto Tecnol=F3gico de Costa=
 Rica.

Next, I have transcribed part of the code from Hugs's Help in Multiple
Parameter Classes and Dependencies Section

---
 module KK where

    class E a b | a -> b, b -> a where
           go    :: a -> b                          -- line 5, personal=
 addition
           back  :: b -> Maybe a                    --         personal=
 addition

---
With the previous declaration Hugs gives me the following message:

        ERROR KK.hs:5 - Haskell 98 does not support dependent parameters.

And I tried too:

---=20
  module KK where

    class  C a b where                            -- line 3
       ok :: a -> b
       ko :: b -> Maybe a

---
and Hugs gives me the message:

        ERROR KK.hs:3 - Haskell 98 does not support multiple parameter
classes  =20

Comment:

Hugs 98 User Manual of September 1999, says that the facility of Multiple
parameter type classes already is available in Hugs 98.

Then, how can I use this? =20
 =20
I installed the following files again again (from Web site)
        *       Win32.zip
        *       Win32exes.zip
        *       Hugs98-Feb2001.zip           -- Hugs for Windows 32
        *       Hugs.hlp

Thank you for paying attention to this,
 =20
Javier.
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Javier Torres Salgado			        Panama: (507)770-5042
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Universidad Autonoma de Chiriqui                        (506)551-6503
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Javier Torres Salgado
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Cartago, Costa Rica                  jtorres@ganimedes.cic.itcr.ac.cr
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