On 07/16/2013 04:57 PM, Michael Orlitzky wrote: > > This all works great, except that when there's 20 or so options, I > duplicate a ton of code in the definition of OptionalCfg. Is there some > pre-existing solution that will let me take a Cfg and create a new type > with Cfg's fields wrapped in Maybe? >
For posterity, I report failure =) If I parameterize the Configuration type by a functor, it breaks the DeriveDataTypeable magic in cmdargs. The resulting manual definitions along with the lenses to look inside the Identity functor well exceed the duplicated code from OptionalCfg. Combining the option parsing and config file parsing increases the amount of code in the command-line parser by roughly an equal amount, but in my opinion a worse consequence is that it conflates two unrelated procedures. I very much like this: rc_cfg <- from_rc cmd_cfg <- apply_args let opt_config = rc_cfg <> cmd_cfg ... All things considered the duplicated data structure seems like the least of three evils. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
