[Template-haskell] Module THTraverse

[Derek Elkins]

On Fri, 14 Nov 2003 15:12:41 +1100
Sean Seefried <sseefried at cse.unsw.edu.au> wrote:

> I could see this task being repeated over and over again, so I did
> what any good programmer would do and wrote a module to relieve the
> burden of writing the recursive cases, which I have called
> THTraverse.

I'm sure plenty have seen it.  I was going to handle this with
updateable fold algebras as well as get TH to generate them*,
but the GHC "Scrap Your Boilerplate" support seemed to take away much of
the motivation.  It seems a much quicker way to 'do' THTraverse is
simply to add deriving (Data,Typeable) to the TH data types or, less
mutatively, to have a module with the instances.  I think this has been
mentioned before, though I may be thinking of somewhere else.  At any
rate, I've thought about it before.

* I actually have a handwritten one for datatypes.