transformers versus mtl

Brandon S. Allbery KF8NH allbery at
Tue Mar 24 21:22:35 EDT 2009

On 2009 Mar 24, at 20:36, Alexander Dunlap wrote:
> I'm pretty sure all monads are functors.

All monads are functors, but IIRC not all Monads are Functors.  But  
Monad includes a liftM which is the same as Functor's fmap (usually?  
something tickling me about possibly the list Monad?) so in fact you  
*could* synthesize a Functor from atop a Monad that isn't already a  

brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allbery at
system administrator [openafs,heimdal,too many hats] allbery at
electrical and computer engineering, carnegie mellon university    KF8NH

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