#9537: concatMap is not a good producer for list fusion -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: ekmett Type: bug | Status: patch Priority: normal | Milestone: 7.10.1 Component: Core | Version: 7.9 Libraries | Keywords: fusion Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: Runtime | Related Tickets: performance bug | Test Case: | Blocking: | Differential Revisions: Phab:D348 | -------------------------------------+------------------------------------- Changes (by dfeuer): * cc: core-libraries-committee@… (added) * status: new => patch * differential: => Phab:D348 Old description:
Joachim Breitner raised this issue in an [http://www.haskell.org/pipermail/haskell-cafe/2011-December/097228.html email to haskell-cafe] in 2011, but he never got a response. For some reason, list comprehensions desugar to `concatMap` forms written to fuse, but the actual `concatMap` function is not written so. Unless there is a good reason for this, we should make it fuse.
New description: Joachim Breitner raised this issue in an [http://www.haskell.org/pipermail /haskell-cafe/2011-December/097228.html email to haskell-cafe] in 2011, but he never got a response. For some reason, list comprehensions desugar to `concatMap` forms written to fuse fully, but the actual `concatMap` function is not written so. Unless there is a good reason for this, we should make it fuse better. -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9537#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler