Re: [Haskell-cafe] Avoiding boilerplate retrieving GetOpt cmd line args

27 Jul 2007

      Hi

Why not:
...
data Flag
  = Filter String
  | DateFormat String
  | DocStart String
  | DocEnd String
Becomes:

data Flag = Flag Key String
data Key = Filter | DateFormat | DocStart | DocEnd

getString :: Flag -> Key -> String
getString (Flag x y) key = if key == x then y else ""

You can easily extend this to defaults:

defaults = [(DocStart,"1")]

then lookup, instead of just "" as the else clause.

If you have to use Data/Typeable you will no longer be writing
portable Haskell, and while they are great, they aren't the thing to
use here.

Thanks

Neil

Re: [Haskell-cafe] Avoiding boilerplate retrieving GetOpt cmd line args

Neil Mitchell