#9398: Data.List.cycle is not a good producer -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.8.4 Component: libraries/base | Version: 7.8.3 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Easy (less than 1 | Type of failure: Runtime hour) | performance bug Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Data.List.cycle is not a good producer. I'm not at all sure this solution is the best, but it allocates much less when mapped over and then folded. If we could make it a good consumer cheaply that would be nice too, but I imagine it's probably mostly applied to short lists, so that is probably not a priority. {{{#!hs {-# INLINE cycle #-} cycle :: [a] -> [a] cycle [] = error "Prelude.cycle: empty list" cycle xs = concat $ repeat xs }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9398 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler