-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 06.04.2014 10:09, Herbert Valerio Riedel wrote:
On 2014-04-06 at 00:33:34 +0200, Henning Thielemann wrote:
Am 06.04.2014 00:27, schrieb Niklas Haas:
This already exists in the form of
sortBy . comparing
Not exactly, because sortByKey memorizes the results of 'f' and (sortBy . comparing) recomputes 'f' all the time.
...what about a RULE that replaces "sortBy . comparing" by an internal non-exported "sortByKey"?
How does GHC give evidence to the programmer that RULEs actually applied? How do you argue to the user of Data.List that there is no need to implement a (memoizing) sortByKey since GHC will do the right thing for him if he uses sortBy . comparing instead? As long as RULEs remain some (practically) invisible compiler magic, as long as I have a way to declare that in certain situations certain rules absolutely MUST fire, I can put no trust in the whole RULEs mechanism. Cheers, Andreas - -- Andreas Abel <>< Du bist der geliebte Mensch. Department of Computer Science and Engineering Chalmers and Gothenburg University, Sweden andreas.abel@gu.se http://www2.tcs.ifi.lmu.de/~abel/ -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iEYEARECAAYFAlNBEVkACgkQPMHaDxpUpLPaIgCg1SuQLD9lHoVrGpgIcFipQ/9Q 7MUAn2C5w2/wgpvyGoJOEjg7hMeLNVrk =zunq -----END PGP SIGNATURE-----