The compose-trans package
A version of monad transformers that (a) allows one to convince the type checker that transformer application is a monad, and (b) doesn't need lots of boilerplate to add a new transformer. It's supposed to play nicely with Control.Monad.Trans.
In order to make a new transformer (say, T) an instance of TransM (TransP, TransF) class, all you have to do is:
define instance MonadTrans T — which you've probably done already
define instance Monad m => Monad (T m) — also something quite common (for TransP and TransF you'd need another instance for MonadPlus and MonadFix, respectively).
write instance Trans T where transMInst = instM — which is exactly one line of boilerplate. Sorry for that.
After that, you can use your new and shiny transformer in compositions, like ReaderT Char :. T :. WriterT String — and such a composition would automagically become a monad transmormer.
- No changelog available
|Dependencies||base (>=2 && <=4), mtl|
|Upload date||Mon Aug 17 04:13:54 UTC 2009|
- compose-trans-0.0.tar.gz [browse] (Cabal source package)
- Package description (included in the package)
For package maintainers and hackage trustees