On 07/23/2013 11:48 PM, wren ng thornton wrote: > On 7/23/13 9:01 PM, Michael Orlitzky wrote: >> Obviously not what I want! Has anyone >> else run into this? Figured out a workaround? > > I haven't run into this specific problem, but I do have a sort of > workaround. Whenever dealing with CmdArgs (or any similar system) I > typically define *two* record types. > > The first one just gets the raw input from CmdArgs; no more, no less. > Thus, for your issue, this record would use String. For other issues > mentioned recently about optionality, this record would use Maybe. > > The second one is the one actually used by the program as the > configuration object. This one is generated from the first by performing > various sanity checks, filling in defaults, converting types from their > CmdArgs version to the version I actually want, etc. > > IME, regardless of language, trying to conflate these notions of an > external-facing parser-state and an internal-facing configuration-record > just causes problems and accidental complexity. It's best to keep them > separate IMO. >
It's not the internal configuration and command-line arguments that I wanted to share, but rather the config /file/ and command-line arguments. Those two are then mashed together into the real configuration data structure at run time. The reason for the newtype is for the config file parsing -- without the newtype, I'm forced to create orphan instances like some kind of animal =) In any case, this turned out to be a real bug and not the usual user error. Neil was nice enough to fix it, and it looks like it already hit hackage, so I'm gonna go give it a shot! _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
