Data.Fixed (in base) has been updated with Data instances in HEAD. When that's released, I'll release time-extra that will contain Data instances. I've got it all ready to go. The reason Data instances are in time-extras is that the time library must be Haskell 98, while Data instances require Rank2. -- Ashley On Wed, 2009-10-21 at 11:15 -0500, Thomas Hartman wrote:

update:

on haskell reddit, dons suggested simply patching time. reasonable enough, but I hit a glitch where the Data.Fixed (in base lib) was missing a Data instance, and gave up when I couldn't find the source repo for base. Is this simply part of ghc?

Anyways, that instance seems to be added in ghc 6.12 so probably a non issue now or closer to it.

http://www.haskell.org/ghc/dist/current/docs/html/libraries/base/Data-Fixed....

also, aavogton #haskell suggested

http://hpaste.org/fastcgi/hpaste.fcgi/view?id=11009#a11009

as a workaround for people using time on happstack earlier than 6.12, probably nicer than the MyTime hack I created though it comes with a bit more baggage.

I haven't upgraded to 6.12 but I would suggest that time now be made Data Generics friendly if it hasn't already, since this is probably a very simple change and would be helpful to happstack. If no one has time to do this I'll try to get around to it when I upgrade to 6.12.

Also wouter swierstra suggested that standalone deriving ( http://www.haskell.org/ghc/docs/latest/html/users_guide/deriving.html#stand-... ) could be helpful in this case but I'm not sure why, or even whether this was for data-izing data.time or system.time or both.

Given all this I won't be uploading anything to hackage, and hopefully the base libs + time will be data friendly soon enough.

thomas.

2009/10/19 Thomas Hartman :

...

At

http://osdir.com/ml/haskell-cafe@haskell.org/2009-10/msg00197.html

I griped that the lack of Data-Derivable time values was causing me headache in happstack.

In the proposed cabal package

http://patch-tag.com/r/tphyahoo/systemtimetypeable/snapshot/current/content/...

I submit a workaround that, while probably not the ideal thing, has proved helpful to me.

Basically, I use the type MyTime, which is data-deriveable, when working with Macid in happstack; and convert from System.Time and/or Data.Time with the accompanying utility functions when necessary. Perhaps the utility functions are useful on their own as well. I found it surprisingly hard to get from Data.Time values to System.Time values.

Anyways, I am interested in what others think and, of course, patches and suggestions welcome.

thomas.