Re: [Haskell-cafe] a problem defining a monad instance

Petr Pudlak wrote:

The problem is the (Ord b) condition, which is required for the Map functions. When I try to define the monad instance as

...

instance Monad Distrib where return = dreturn (>>=) = dcompose

obviously, I get an error at (>>=): Could not deduce (Ord b) from the context.

This is the same reason we do not have e.g. a Monad instance for Set. One solution is a concept of "restricted" monads, and one implementation of restricted monads is given here: http://okmij.org/ftp/Haskell/types.html#restricted-datatypes - Jake