GHC and Haskell 98

Simon Marlow marlowsd at
Fri Jun 24 13:35:12 CEST 2011

On 17/06/2011 16:42, Brandon Allbery wrote:
> On Fri, Jun 17, 2011 at 11:11, Jacques Carette<carette at>  wrote:
>> they chose to stick to pure Haskell 98.  Plan B is actually more fragile in
>> that respect, in that if they forget to be really really explicit about
>> their code being pure Haskell 98, the resulting compilation errors do not
>> make it obvious that that is actually the problem.  This will in fact only
>> get worse as time goes by.
> This is a very good point that is glossed over by the proposal:  is
> Haskell 98 the default or is the current Haskell standard the default,
> and how do we handle existing code bases that might be broken by
> incompatible changes (the point of this discussion)?  It's really the
> same question seen from a higher level.

When you're using Cabal, there's no "default", because all package 
dependencies are specified explicitly.

When using standalone GHCi or ghc the plan A default would be

   - LANGUAGE Haskell2010
   - -package base

whereas currently (GHC 7.0) it is

   - LANGUAGE Haskell2010
   - -package base -package haskell98

which is already a bit weird.

We could make it

   - LANGUAGE Haskell2010
   - -package haskell2010

but that would confuse a lot of people for negligible gain.


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