[Haskell-cafe] Re: Adding Ord constraint to instance Monad Set?
| Constraints on datatype declarations are a misfeature of Haskell, and | have no useful effect. | | Is this the final conclusion? Yes, it is, I believe. Constraints on data type declarations are a mis-feature. I tried to get them removed, but there was some argument that they could be made useful (see John Hughes's paper Restricted data types in Haskell, Haskell workshop 1999), and they stayed. Simon Made useful in a way that would solve the problem in this thread, I might add. The paper is at http://www.cs.chalmers.se/~rjmh/Papers/restricted-datatypes.ps for the curious. John ___ Haskell-Cafe mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Adding Ord constraint to instance Monad Set?
On Wed, 31 Mar 2004, Tomasz Zielonka wrote: You can try to define a different version of Monad using multiparameter type classes, something like: class M m a b where (=) :: m a - (a - m b) - m b I don't think this works. GHC can't deduce context for (). I don't understand why, but I've tried a variety of permutations of constraint declarations (m b needs to be a Monad as well...). -Alex- _ S. Alexander Jacobson mailto:[EMAIL PROTECTED] tel:917-770-6565 http://alexjacobson.com ___ Haskell-Cafe mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell-cafe
