[Haskell-cafe] GetOpt

[Bulat Ziganshin]

Hello Tomasz,

Thursday, April 27, 2006, 4:45:45 PM, you wrote:

> On Thu, Apr 27, 2006 at 03:10:32PM +0400, Bulat Ziganshin wrote:
>> i don't like the GetOpt interface (it returns a list of options what
>> is unusable for high-speed application)

> This got me interested. I assume that you measured performace and it
> wasn't fast enough.

no, i abandoned this without testing :)

you misunderstood me, though - i mean speed of using this list. if
some internal function need option "foo", it should scan the entire
list to find it's value. so i (like you, i think) save the result of
option parsing in the structure. and because i anyway need the way to
extract options from list and store them into structure - i
implemented my own set of functions to recognize options too.

ultimately, the main problem of all options-parsing stuff i ever seen,
is requirement to repeat option definition many times. if i have, say,
40 options, then i need to maintain 3 to 5 program fragments that deal
with each option. something like this:

data Options = Options { r :: Bool,
                         x :: Int
                         ....
                       }

options = { "r", "description"
            ....
          }

main = do list <- getOpts options cmdline
          let options = Options { r = findBoolOption list "r",
                                  x = findIntOption list "x",
                                  ....
                                }

each change in options list mean that i should find all these places
and correct them. PescoCmd may be does something against this problem,
i don't remember why i was pleased by this library

as far as i see, solving of this problem is impossible in Haskell
itself, we need some form of preprocessing, probably with TH. this
should allow us to write something like this:

$(optionProcessor [("r", "description", `Bool, .....)
                  ,("x", .....
                  ...
                  ]
)

what will generate all the stuff above

as i already said, you can find module Cmdline in my program, that
is not ultimate solution, but at least it somewhat simplified my work
                  

-- 
Best regards,
 Bulat                            mailto:Bulat.Ziganshin at gmail.com