Re: [Haskell-cafe] Language complexity & beginners (Was: New type of ($) operator in GHC 8.0 is problematic)

Hi, I understood one more point. (I share here.) The Prelude library document for ghc 8.0 is already well described for beginners/newcomers. * The ($)'s signature of 8.0.1 is already simple (not include forall ...). * The Bool's kind of 8.0.1 is already represented with "TYPE Lifted" (changed from '*'). ghc7.8.4 [1]: data Bool :: * foldr :: (a -> b -> b) -> b -> [a] -> b ($) :: (a -> b) -> a -> b ghc7.10.4 [2]: data Bool :: * foldr :: (a -> b -> b) -> b -> t a -> b ($) :: (a -> b) -> a -> b ghc8.0.1-rc2 [3]: data Bool :: TYPE Lifted foldr :: (a -> b -> b) -> b -> t a -> b ($) :: (a -> b) -> a -> b [1] https://downloads.haskell.org/~ghc/7.8.4/docs/html/libraries/base-4.7.0.2/Pr... [2] https://downloads.haskell.org/~ghc/latest/docs/html/libraries/base-4.8.2.0/P... [3] https://downloads.haskell.org/~ghc/8.0.1-rc2/docs/html/libraries/base-4.9.0.... Regards, Takenobu 2016-02-08 19:08 GMT+09:00 Takenobu Tani :

Hi Richard and devs,

What a wonderful (#11549) ! This is a beautiful solution for beginners/newcomers. Beginners will not confuse and they can gradually go ahead.

I extremely appreciate that you are continuously improving the ghc for us.

Thank you very much, Takenobu

2016-02-07 0:17 GMT+09:00 Richard Eisenberg :

...

I have made a ticket #11549 ( https://ghc.haskell.org/trac/ghc/ticket/11549) requesting a -fshow-runtime-rep flag (recalling that the name levity will soon be outdated) as described in this thread. I will make sure this gets in for the release of 8.0.

Other points:

- You're quite right that (.) could be generalized. But I'll wait for someone to really want this.

- I don't have a non-contrived example of the use of ($) with unlifted types. It's quite possible that when adding the dirty runST hack, it was observed that an unlifted type would be OK. At that point, the type of ($) didn't need to become so elaborate. And now we're just trying not to change old (but perhaps unrequested) behavior.

- For the record, this debate is entirely unrelated to the runST impredicativity hack. (Except, as noted above, perhaps in history.) That hack remains, basically unchanged.

- On Feb 6, 2016, at 9:55 AM, Roman Cheplyaka wrote:

...

I would call this a simplification rather than a lie.

This is a very convincing argument.

- Thanks, also, for the voice of support. What I love about the Haskell community is that we can have an impassioned debate full of strong opinions, and it all very rarely devolves into a proper flame war. All the posts I've seen in this thread have been constructive and helpful. Thanks.

Richard _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe