2008/10/17 Magnus Therning
I wanted to throw in another idea, something I didn't come up with myself but used in omnicodec[1]. Now I don't remember where I picked up the idea:
This method is described in http://www.haskell.org/haskellwiki/High-level_option_handling_with_GetOpt. I have used it in the past and eventually end up with huge Config data structures and not much separation of unrelated parts of the computation. Of course, this is probably just me ;-) Alternatively (and this is where I have had more success) you can take several passes over the command arguments, using different parsers. Each parser just ignores what it doesn't recognise: parseArgs names = do args <- getArgs let info = parseWith infoOptions [] let options = parseWith argOptions defaultOptArgs let query = parseWith queryOptions defaultQuery return (info, options, query) where parseWith os z = case getOpt Permute os args of (o,_,_) -> foldr id z o Note that this method tends to ignore user error at the command line, but I'm sure a hybrid could be constructed that was more chatty but still quite clean at the back end. See http://www.dougalstanton.net/code/buses/ for this code in its wider context. Cheers, D -- Dougal Stanton dougal@dougalstanton.net // http://www.dougalstanton.net