the MPTC Dilemma (please solve)

[isaac jones]

I've created a wiki page and a ticket to record solutions to what I'm
calling the "Multi Parameter Type Class Dilemma".  It's summarized
thusly:

MultiParamTypeClasses are very useful, but mostly in the context of
FunctionalDependencies. They are particularly used in the monad
transformer library found in fptools. The dilemma is that functional
dependencies are "very, very tricky" (spj). AssociatedTypes are
promising but unproven. Without a solution, Haskell' will be somewhat
obsolete before it gets off the ground.

I've proposed a few solutions.  Please help to discover more solutions
and/or put them on the ticket/wiki.  

Wiki page:
http://hackage.haskell.org/trac/haskell-prime/ticket/90

Ticket:
http://hackage.haskell.org/trac/haskell-prime/wiki/MultiParamTypeClassesDilemma


peace,

  isaac



-- 
isaac jones <ijones at galois.com>