Hello Iavor, Tuesday, March 21, 2006, 9:38:06 PM, you wrote:
whenM :: Monad m => m Bool -> m a -> m () ID> One thing about 'whenM' however is that to implement it I'll need to ID> add an extra ID> 'return ()' to the parameter computation. This is probably not a big deal, but ID> given that most of the time the computation used in 'whenM' is already ID> of type 'm ()', I wonder if leaving it to the programmer to add the ID> 'return ()' is not a better idea. ID> What do you think?
that is a sort of thing that bother me constantly. `when` has the same problem. i as application programmer want to write less unnecessary code ID> Note however that 'monadLib' is not a drop in replacement for 'mtl', ID> as other things differ as well, for example 'monadLib' has a different ID> monad class hierarchy. class hierarchy don't matter for application programs in most cases. may be it's better to have "mtl emulation module" and give it (in ghc 6.6) the same name as mtl module has currently. so new apps will use your library directly and other apps will use it through emulation. i use the same technique for my own Binary-replacing module
deriving Typeable for everything would be good too. ID> I have never used 'Typeable', but perhaps I will take a look. I would ID> like 'monadLib' to stay simple, but if people use 'Typeable' on ID> monadic computations I could probably add some instances. Are there ID> any examples of when it is useful to do things like that? Does Hugs ID> support Typeable?
i think that support for Typeable in any library is a "good form" now, like support for monads itself :)
Also, it looks like some of your monads overlap with what is provided by the Applicative (Idiom) and friends classes to be included in the next version of ghc, perhaps you can make a version of monadLib that builds on those? ID> I am aware of that, and once they are released I will probably make ID> use of them, because I think that they have some nice ideas. In the ID> mean time however 'monadLib' provides 'Monad.ForEach' and ID> 'Monad.Combinators'.
i think that it's better not to wait while they will be released, but after your MonadLib will be stabilized, propose to include it in 6.6 and develop version of lib that is compatible with 6.6 (if your library goal is to replace mtl) -- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com