On Mon, 12 Jan 2009, Wolfgang Jeltsch wrote:
Hello,
it?s already problematic, that State, StateT etc. are under Control.Monad. While they are monads, they are also applicative functors, for example. And some ?monad transformers? are also applicative functor transformers and probably all of them are functor transformers. There are situations where you want to use these types only as applicative functors, for example when composing context-free parsers.
I already posted something similar, with no response: http://www.haskell.org/pipermail/libraries/2007-October/008274.html Maybe this time is better?
During this restructuring, we could also rename State to StateTrans since values of State are not states but state transformers.
Right, I also like to use 'state' as identifier for a state, not for a stateful action. And I was confused, by Reader not being really a counterpart to Writer. If I want to read, what I wrote with Writer, I usually have to use a State monad, not Reader. 'Context' or 'Environment' seems to be a better name for 'Reader'.