Question about Haskell AST

[Jane Ren]

Hi Max,

I tried adding "extensionFlags = Opt_Cpp" to dflags, but I still got the same error.

When you mentioned 
"You might have to iterate a few times to find the correct set of flags.", 
did you mean trying out all the "data ExtensionFlag" flags in compiler/main/DynFlags.hs and find a subset that works?

data ExtensionFlag
   = Opt_Cpp
   | Opt_OverlappingInstances
   | Opt_UndecidableInstances
   | Opt_IncoherentInstances
    ...

Thanks
Jane
________________________________________
From: omega.theta at gmail.com [omega.theta at gmail.com] On Behalf Of Max Bolingbroke [batterseapower at hotmail.com]
Sent: Tuesday, January 25, 2011 1:34 AM
To: Jane Ren
Cc: Simon Peyton-Jones; glasgow-haskell-users at haskell.org
Subject: Re: Question about Haskell AST

On 24 January 2011 17:20, Jane Ren <j2ren at ucsd.edu> wrote:
> When I try this, I get
> "AstWalker: panic! (the 'impossible' happened)
>  (GHC version 7.0.1 for x86_64-apple-darwin):
>        lexical error at character 'i'

It looks like you need to add the CPP extension to the DynFlags:

  setSessionDynFlags dflags { extensionFlags = Opt_Cpp : extensionFlags dflags }

You might have to iterate a few times to find the correct set of flags.

Cheers,
Max