Claus Reinke:
however, the underlying problem is not limited to MPTCs, and FDs are not the only attempt to tackle the problem. so I agree with Isaac: getting a handle on this issue is imperative for Haskell', because it will be the only way forward when trying to standardize at least those of the many extensions that have been around longer than the previous standard Haskell 98. and if Haskell' fails to do this, it fails.
Please keep things in perspective: (A) It's not as if every interesting program (or even the majority of interesting programs) use(s) MPTCs. (B) I don't think the time for which an extension has been around is particularly relevant. One of the big selling points of Haskell is that it's quite well defined, and hence, its semantics is fairly well understood and sane - sure, there are dark corners, but compared to other languages of the same size, we are in good shape. If we include half-baked features, we weaken the standard. In fact, it's quite worrying that FDs have been around for so long and still resisted a thorough understanding. Manuel