On Fri, 29 Apr 2005, Simon Peyton-Jones wrote:
2. Use sub-typing, so that a value (Left x) is *both* in type Either and in type NEither. This opens a very large and complicated design space, as Ben mentioned.
I've been playing with this design space for a while and think there's at least one reasonable solution in it - I'm slowly piecing together a paper, though personal circumstances're causing this to take quite some time (#haskellers will have heard much of this before in chan). If you avoid doing anything too strenuous with records and maintain some reasonably simple restrictions, you only need annotations to disambiguate 'multiple inheritance'-like scenarios and _ patterns. -- flippa@flippac.org "My religion says so" explains your beliefs. But it doesn't explain why I should hold them as well, let alone be restricted by them.