15 Feb
2011
15 Feb
'11
7:48 a.m.
On Monday 14 February 2011 19:23:43, Britt Anderson wrote:
Actually, I can load the module and I have mtl. I just don't understand why I can use State as a data constructor, but the inverse of runState, i.e. state works just fine. Has this library/package been reconfigured from when most people were writing tutorials?
Exactly that. As of mtl-2.*, mtl is now a wrapper around transformers and no longer an independent library. One change which broke a lot of tutorials (and some code) is that State is no longer a separate datatype. (State s) is now a type synonym for (StateT s Identity), similarly for Reader, Writer. Those parts of the tutorials whcih don't use the data-constructor should work unchanged, though.