Re: [Haskell] Re: Re: RE: Extensible records: Static duck typing
[Redirecting to haskell-cafe] Ben Franksen wrote:
TREX seems to be generally agreed to be too complicated to implement and explain.
What evidence do you have for this? Speaking as somebody who implemented Trex for Hugs (and who also witnessed Ben Gaster build an independent implementation), I'd have to disagree about the first part of this. As I recall, the implementation was reasonably straightforward, and wasn't any more complicated than other common type system extensions that I've worked on. I'm also not sure why you think it is complicated to explain, but I suppose that's even more subjective. One of the most difficult things about the Trex implementation was finding a syntax that meshed nicely with the rest of the Haskell syntax. This is likely to be a problem for any record system extension of Haskell---unless you're prepared to accept a more unconventional syntax---because many of the symbols that you might want to use ({, }, ., |, \, for example) have already been adopted for other purposes. Ah, syntax! All the best, Mark
Mark P Jones wrote:
Ben Franksen wrote:
TREX seems to be generally agreed to be too complicated to implement and explain.
What evidence do you have for this?
Not much, I have to admit that. It basically seems to be SPJ's opinion, as he writes in his proposal that he "never got around to implementing [TREX] in GHC. Why not? Mainly because the implementation cost turned out to be relatively high" and further claims his new proposal "is considerably simpler to implement, and [...] it is rather simpler to explain." I also had the impression from earlier discussions that there are few people who support the TREX idea. I could be completely wrong, though.
Speaking as somebody who implemented Trex for Hugs (and who also witnessed Ben Gaster build an independent implementation), I'd have to disagree about the first part of this. As I recall, the implementation was reasonably straightforward, and wasn't any more complicated than other common type system extensions that I've worked on. I'm also not sure why you think it is complicated to explain, but I suppose that's even more subjective.
I did not say, nor did I want to imply, that this is my own opinion. I would be extremely happy to have TREX in ghc and all the other implementations, I just fear that it is not going to happen, at least not any time soon. In fact I am almost completely un-biased as to which record system Haskell gets, as long as DOES get one and preferably IN MY LIFETIME. I'd give up a serious amount of expressive power if it brings us nearer to this goal. Maybe this is just me being short-sighted and egotistical.
One of the most difficult things about the Trex implementation was finding a syntax that meshed nicely with the rest of the Haskell syntax. This is likely to be a problem for any record system extension of Haskell---unless you're prepared to accept a more unconventional syntax---because many of the symbols that you might want to use ({, }, ., |, \, for example) have already been adopted for other purposes. Ah, syntax!
Oh yes, that is indeed quite hard. One more reason for me to a prefer a simpler system. Cheers Ben
participants (2)
-
Ben Franksen -
Mark P Jones