[Haskell-beginners] Strange new Haskell Platform

bucephalus org bucephalus.org at gmail.com
Thu Sep 20 10:18:26 CEST 2012

Dear fellow Haskellers,

last weak my Linux machine broke down and refused to start again. I bought
a new one and installed a fresh new KDE/Linux distribution (Mint/Ubuntu)
and it looks and feels awesome. I also installed the Haskell platform via
the default GUI installer (mintInstall).
But when I try to run my recovered Haskell modules again, strange things

First of all, I have a module that has a line
  import System
and that used to be fine. But now, when I try to load the module in a ghci
session, I get a complaint:
  Could not find module 'System'
  It is a member of the hidden package 'haskell98-'
The same happens if I do a
  Prelude> :m System
What is going on?

Secondly, I have another module that has a data type definition like this
  data (Show n, Show v, Ord n, Ord v) => Automaton n v = Automaton {
     nameSet :: Set.Set n,
     valueSet :: Set.Set v,
  } deriving (Show, Eq, Ord)
and that used to work fine, too. But now, I get the complaint
  Illegal datatype context (use -XDatatypeContexts): (Show n, Show v, Ord
n, Ord v) =>
But when I follow the advice and start the module file with a
  {-# LANGUAGE DatatypeContexts ... #-}
I got the opposite complaint:
  Warning: -XDatatypeContexts is depracated: It was widely considered a
misfeature, and has been removed from the Haskell language.
How can I clean this up?

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