14 Apr
2011
14 Apr
'11
9:20 a.m.
On Thu, Apr 14, 2011 at 03:02:18PM +0200, Daniel Fischer wrote:
Alas, Functor is not a superclass of Monad, so a Monad constraint is not more restrictive than a Functor constraint.
Yes, that is the issue -- as those classes are now, making this change would break programs. Several functions are affected by the same issue: ReaderT: ask asks StateT: evalStateT execStateT get put gets liftListen liftPass WriterT: execWriterT tell listen listens pass censor It's particularly annoying for ReaderT and WriterT, now that they're Applicative transformers as well as Monad transformers.