patch applied (cabal): Change handling of bool command line args to allow an unset state

[Malcolm Wallace]

> Tue Apr 29 13:11:23 PDT 2008  Duncan Coutts <duncan at haskell.org>
>   * Change handling of bool command line args to allow an unset state
>   For bool valued flags we were always producing the command line
>   string corresponding to a false flag value, even if the flag was
>   not set. For example we'd always get "--disable-shared".
>   It is important for cabal-install to be able to take an empty set
>   of flags, override a few flags and turn the flags back into
>   command line strings without getting a lot of extra defaults.
>   Partly this is because we have to work with older versions of the
>   Cabal library command line which does not recognise the new options.

This patch breaks the nhc98 build of Cabal.  Here is the error:

  $ /Users/malcolm/Haskell/nhc98/script/nhc98 -c Distribution/Simple/Command.hs
  nhc98comp: The class Prelude.Functor has no instance for the type Prelude.->.
  Possible sources for the problem are: 189:72-189:75
  When type checking declarations at: 189:1-189:81
    
And the offending lines of the patch:

    hunk ./Distribution/Simple/Command.hs 188
    -boolOpt' :: (b -> Bool) -> (Bool -> b) -> OptFlags -> OptFlags -> MkOptDescr (a -> b) (b -> a -> a) a
    -boolOpt' g s ffT ffF _sf _lf d get set = BoolOpt d ffT ffF (set.s) (g.get)
    +boolOpt' :: (b -> Maybe Bool) -> (Bool -> b) -> OptFlags -> OptFlags -> MkOptDescr (a -> b) (b -> a -> a) a
    +boolOpt' g s ffT ffF _sf _lf d get set = BoolOpt d ffT ffF (set.s) (g `fmap` get)

Regards,
    Malcolm