[Haskell-cafe] Re: derive & Drift - some help please

Well you can do

deriving instance Typeable LocalType

etc. if you enable the DeriveDataTypeable and StandaloneDeriving extensions. You will get other error messages for missing instances; just keep adding

deriving instance Typeable Day

etc. Eventually, you will need to implement an instance by hand for Pico, because Pico's data constructors are not exported from Data.Fixed. I'm not very familiar with Data and Typeable so I can't help you there, but you can probably look at some existing instances for help. Hope that's useful for you. Alex On Sun, Mar 8, 2009 at 12:40 PM, Gü?nther Schmidt wrote:

Hi Alexander,

well I have this:

newtype AdmissionDate = AdmDt LocalTime        deriving (Data,Typeable ..)

at least that's where I wonna get.

I don't know how to create the proper instance declarations though for LocalTime.

AdmissionDate is an element of a larger data structure, this data structure for instance also has a

newtype DischargeDate = DchrgDt LocalTime        deriving (Data,Typeable ...)

With my haskell work so far I was blessedly free of the need for deriving. Until now ...

Günther

Alexander Dunlap schrieb:

...

What problems are you encountering?

Alex

On Sun, Mar 8, 2009 at 11:58 AM, G?uenther Schmidt wrote:

...

Hi Sterling,

sry, but I can't get it to work.

Günther

Sterling Clover schrieb:

...

You shouldn't need any extra tools for this. A combination of the StandaloneDeriving and DeriveDataTypeable extensions in GHC should suffice.

Cheers, S.

On Sun, Mar 8, 2009 at 10:30 AM, Gü?nther Schmidt mailto:gue.schmidt@web.de> wrote:

  Hi,

  I need to derive Data, Typeable for Data.Time.LocalTime. I had hoped   to use either derive or DrIFT to generate the instance declarations   for it.

  I tried to understand the respective user manuals but it's still all   Greek to me.

  Someone please help!

  Günther

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