| makes (:) look "interesting" to the inliner. Unfortunately, as I | discovered after much extreme puzzlement about why rules relating to | scanl were affecting things that had nothing to do with scanl, it | turns out that making (:) look interesting is really quite bad, and | something that we probably never want to happen. Can you give a concrete, reproducible example of the problem you articulate here? (In general, a concrete example brings tremendous focus to discussions, giving readers something specific to bite on.) Simon | -----Original Message----- | From: ghc-devs [mailto:ghc-devs-bounces@haskell.org] On Behalf Of David | Feuer | Sent: 30 August 2014 23:05 | To: ghc-devs | Subject: cons/build and making rules look boring | | I think I may have figured out at least part of the reason that | cons/build gives bad results. I actually ran into a clue when working | on scanl. It seems at least part of the problem is that a rule like | | x : build g = build (\c n -> c x (g c n)) | | makes (:) look "interesting" to the inliner. Unfortunately, as I | discovered after much extreme puzzlement about why rules relating to | scanl were affecting things that had nothing to do with scanl, it | turns out that making (:) look interesting is really quite bad, and | something that we probably never want to happen. | | As a result, the only ways I see to try to make rules like that work | properly are | | 1. If constructors are *always* best treated as boring, and the | inliner knows when's a constructor, make it treat them all as boring. | | 2. Offer a BORINGRULE annotation to indicate that the rule should not | make its LHS "interesting", or | | 3. (I don't like this option much) Make a special case forcing (:) in | particular to be boring. | | David | _______________________________________________ | ghc-devs mailing list | ghc-devs@haskell.org | http://www.haskell.org/mailman/listinfo/ghc-devs