[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
happen.
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 'haskell98-2.0.0.1'
...
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?
Cheers,
Tom
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