RE: [commit: ghc] master: Add rule mapFB c (λx.x) = c (2fa4421)

Hi, I guess you are right. I should also be more careful about distinguishing Phab DR that I create to get feedback from CI and review, even before I do such non-functional polishing of the patch, and ready-to-apply changes (which I'd commit myself anyways). Joachim Am 8. März 2017 13:22:55 MEZ schrieb Simon Peyton Jones :

Joachim

Please, I beg you, add a comment to explain why this rule is useful. I'm sure you had a good reason for adding it, but it's not apparent from the code.

Thanks

Simon

| -----Original Message----- | From: ghc-commits [mailto:ghc-commits-bounces@haskell.org] On Behalf | Of git@git.haskell.org | Sent: 06 March 2017 23:52 | To: ghc-commits@haskell.org | Subject: [commit: ghc] master: Add rule mapFB c (λx.x) = c (2fa4421) | | Repository : ssh://git@git.haskell.org/ghc | | On branch : master | Link : | https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fghc.ha | skell.org%2Ftrac%2Fghc%2Fchangeset%2F2fa44217c1d9722227297eefb0d6c6aed | 7e128ca%2Fghc&data=02%7C01%7Csimonpj%40microsoft.com%7Cc5db3687da004cd | 11d0f08d464ebc6ca%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C6362444 | 11212143808&sdata=KMHS17MUXQUkBOaMbFiRxXiRM8gIvlEMGz%2FDw7F7Njo%3D&res | erved=0 | | >--------------------------------------------------------------- | | commit 2fa44217c1d9722227297eefb0d6c6aed7e128ca | Author: Joachim Breitner | Date: Mon Mar 6 17:30:52 2017 -0500 | | Add rule mapFB c (λx.x) = c | | Test Plan: exended T2110 with a case for that. | | Reviewers: austin, hvr, dfeuer, bgamari | | Reviewed By: dfeuer | | Subscribers: dfeuer, thomie | | Differential Revision: https://phabricator.haskell.org/D3275 | | | >--------------------------------------------------------------- | | 2fa44217c1d9722227297eefb0d6c6aed7e128ca | libraries/base/GHC/Base.hs | 1 + | testsuite/tests/simplCore/should_run/T2110.hs | 3 +++ | testsuite/tests/simplCore/should_run/T2110.stdout | 1 + | 3 files changed, 5 insertions(+) | | diff --git a/libraries/base/GHC/Base.hs b/libraries/base/GHC/Base.hs | index 2f155c6..6f9d454 100644 | --- a/libraries/base/GHC/Base.hs | +++ b/libraries/base/GHC/Base.hs | @@ -973,6 +973,7 @@ mapFB c f = \x ys -> c (f x) ys | "map" [~1] forall f xs. map f xs = build (\c n | -> foldr (mapFB c f) n xs) | "mapList" [1] forall f. foldr (mapFB (:) f) [] = map f | "mapFB" forall c f g. mapFB (mapFB c f) g = mapFB c | (f.g) | +"mapFB/id" forall c. mapFB c (\x -> x) = c | #-} | | -- See Breitner, Eisenberg, Peyton Jones, and Weirich, "Safe Zero- | cost diff --git a/testsuite/tests/simplCore/should_run/T2110.hs | b/testsuite/tests/simplCore/should_run/T2110.hs | index 610be09..d945fac 100644 | --- a/testsuite/tests/simplCore/should_run/T2110.hs | +++ b/testsuite/tests/simplCore/should_run/T2110.hs | @@ -5,6 +5,8 @@ import Unsafe.Coerce | | newtype Age = Age Int | | +foo :: [Int] -> [Int] | +foo = map id | fooAge :: [Int] -> [Age] | fooAge = map Age | fooCoerce :: [Int] -> [Age] | @@ -19,6 +21,7 @@ same x y = case reallyUnsafePtrEquality# | (unsafeCoerce x) y of | | main = do | let l = [1,2,3] | + same (foo l) l | same (fooAge l) l | same (fooCoerce l) l | same (fooUnsafeCoerce l) l | diff --git a/testsuite/tests/simplCore/should_run/T2110.stdout | b/testsuite/tests/simplCore/should_run/T2110.stdout | index 55f7ebb..4ff957b 100644 | --- a/testsuite/tests/simplCore/should_run/T2110.stdout | +++ b/testsuite/tests/simplCore/should_run/T2110.stdout | @@ -1,3 +1,4 @@ | yes | yes | yes | +yes | | _______________________________________________ | ghc-commits mailing list | ghc-commits@haskell.org | https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fmail.h | askell.org%2Fcgi-bin%2Fmailman%2Flistinfo%2Fghc- | commits&data=02%7C01%7Csimonpj%40microsoft.com%7Cc5db3687da004cd11d0f0 | 8d464ebc6ca%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C6362444112121 | 43808&sdata=y%2BRYDSeV9k2Uj%2BlPtE%2BeIeG05mQvE97QV0B0wgl7cx4%3D&reser | ved=0