On Fri, Jun 5, 2009 at 6:38 PM, wren ng thornton<w...@freegeek.org> wrote:
> > 4) Define a newtype of MyMonadT Parsec and declare instances of MyMonad and > Parsec for it. > > Yes, I know Parsec is (an alias for) a data type, not a type class. But for > the general problem, using newtype wrappers is often the best solution when > it's possible. This is one of the reasons why it's good to define type > classes for specialty monads rather than hard-wiring the types of functions > to use the one concrete instance. (For instance, this is one of the things > that rocks about the LogicT library; you can add a StateT on top of a > MonadLogic and it all works great.) > > > For the actual case of Parsec, you could try defining a GenParser class and > giving it all the combinators as methods, but that's a good deal of work and > may not scale to your task. > If you need a head start: http://community.haskell.org/~aslatter/code/parsec/with_class/ I'm not too happy with what turned out to be the class methods. But I'd need to retire certain parts of the Parsec API to clean it up. Antoine _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
