On Tue, May 24, 2005 at 02:31:29PM -0400, robert dockins wrote:
>
> >>> One of the best bad example is the use of boolean as arguments.
> >>
> >>Oh, yes. That's a pet peeve of mine. About 99% of boolean arguments
> >>should be meaningful two-valued enumerated types. It's literally a
> >>one-liner to create such an enumerated type, so there's no excuse.
> >
> >
> >The documentation effect and type safety provided by two-valued
> >enumerated types is indeed much greater. But one needs a conversion from
> >Bool to the enumeration if one wants to pass the result of a logic
> >operation to the function. What about records with named fields,
> >especially if more options are needed?
> >
> >data CreateDirectoryOptions = Cons {createParents :: Bool}
> >
> >createDirectory (Cons {createParents = True}) "dir"
I think it is easier just to declare it as Enum..
data ParentsFlag = DontCreateParents | CreateParents
deriving(Enum)
now (toEnum . fromEnum) will convert between ParentsFlag and Bool.
John
--
John Meacham - ⑆repetae.net⑆john⑈
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