Monomorphism, monomorphism...

Marcin 'Qrczak' Kowalczyk
10 Oct 2001 10:59:46 GMT

09 Oct 2001 13:55:04 -0700, Carl R. Witty <> pisze:

> The TREX paper from Mark Jones and Benedict Gaster (I hope I
> have the names right) had both extensible records and extensible
> variants (extensible variants being what you would need to implement
> downcasts),

I don't think so. Here is how the requirement can be formulated:

We need some type T such that it's possible to define a family of
functions for arbitrary choices of A:
    upA   :: A -> T
    downA :: T -> Maybe A
satisfying downA (upA a) = Just a. We want to choose the type for T
before deciding the exact set of types for A.

 __("<  Marcin Kowalczyk *
  ^^                      SYGNATURA ZASTĘPCZA