#9495: Do What I Mean RULES for foldr2 look shady -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: Type: bug | Status: new Priority: highest | Milestone: 7.8.4 Component: | Version: 7.8.3 libraries/base | Keywords: Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: Runtime | Related Tickets: crash | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Changes (by dfeuer): * priority: normal => highest * milestone: => 7.8.4 Comment: I'm elevating the priority because it causes an ''undocumented'' reduction in laziness depending on optimization flags. Changing the documentation would lower the priority. Note: if eliminating the DWIM non-confluent rules is considered too much of a breaking change, we can fix the semantics, at least in part, by changing the baseline definition of `foldr2`, and making sure the documentation matches. Specifically, make the first base case look like {{{#!hs foldr2 c n [] ys = ys `seq` n }}} I'm not sure if the rewritten version will end up with the ''same'' semantics, but I'm pretty sure it won't be ''less'' defined, which is the current situation. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9495#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler