14 Oct
2007
14 Oct
'07
8:12 p.m.
Hi Dan, I wrote:
That "monad" really is broken - it's not a monad at all.
Dan Piponi wrote:
Depending on your point of view, ListT isn't broken. It correctly transforms commutative monads into monads.
Interesting. What do you mean by a "commutative monad"? It can't be a monad with some sort of additional commutative law, because the old ListT doesn't even satisfy the monad laws. Or does it in some sense?
The replacement ListT is usually the monad transformer I need when I want a List-like monad transformer, so I'm all for it being in (the standard prelude) mtl.
OK. I take this as a +1 vote for the rewrite.
But it seems sad there isn't a place for the old one to live.
OK, do you propose that we keep it and change its name? -Yitz