Re: [nhc-bugs] nhc98 1.14 FFI issues

11 Sep 2002


      Malcolm Wallace  wrote,
...
Manuel M T Chakravarty  writes:
...
...
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======	Errors after type inference/checking:
  No default for  Parsers.Token at 282:3.(1378,[(173,1432)])
  No default for  Parsers.Token at 254:32.(1267,[(173,1433)])
  No default for  Parsers.Token at 223:1.(1061,[(173,1188)])
  No default for  Parsers.Token at 204:25.(1180,[(173,1187)])
I don't see how this applies to my code (ie, I don't think
the DMR comes in anywhere).
It is possible that the source of nhc98's difficulty is the use of
existential types, e.g.
data Token t =>
         Parser a t r = forall q. Parser (Action a t q r) (Cont a t q)
although I can't verify this hypothesis at the moment.
Hmm, ok.  Unfortunately, there is no way around the
existentials here.
...
...
It's fine for nhc98 to implement extensions to
H98, but they should only be activated when a special
command line option is given.
Indeed.  However, I would point out that your code is already using
extensions to Haskell'98, so you would already have had this flag
switched on.
Which is why I also don't like GHC's all-extensions-or-none
strategy.  It is better when extensions can be enabled
individually.

Cheers,
Manuel