Hello,
what is the state with the semantic specification of GADTs? I am wondering
if they fit in the usual CPO-style semantics for Haskell, or do we need
some more exotic mathematical structure to give semantics to the language.
-Iavor
On Sun, May 8, 2016 at 8:36 AM, Carter Schonwald wrote: On Sunday, May 8, 2016, Richard Eisenberg On May 7, 2016, at 11:05 PM, Gershom B an attempt (orthogonal to the prime committee at first) to specify an algorithm for inference that is easier to describe and implement than
OutsideIn, and which is strictly less powerful. (And indeed whose
specification can be given in a page or two of the report). Stephanie Weirich and I indeed considered doing such a thing, which
conversation was inspired by my joining the Haskell Prime committee. We
concluded that this would indeed be a research question that is, as yet,
unanswered in the literature. The best we could come up with based on
current knowledge would be to require type signatures on: 1. The scrutinee
2. Every case branch
3. The case as a whole With all of these type signatures in place, GADT type inference is indeed
straightforward. As a strawman, I would be open to standardizing GADTs with
these requirements in place and the caveat that implementations are welcome
to require fewer signatures. Even better would be to do this research and
come up with a good answer. I may very well be open to doing such a
research project, but not for at least a year. (My research agenda for the
next year seems fairly solid at this point.) If someone else wants to
spearhead and wants advice / a sounding board / a less active co-author, I
may be willing to join. Richard This sounds awesome. One question I'm wondering about is what parts of
the type inference problem aren't part of the same challenge in equivalent
dependent data types? I've been doing some Intersting stuff on the latter
front recently. It seems that those two are closely related, but I guess there might be
some complications in Haskell semantics for thst? And or is this alluded to
in existing work on gadts? _______________________________________________
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