#8704: Use GHC.Exts.build in randoms, randomRs to achieve fusion -------------------------------------+------------------------------------ Reporter: ion1 | Owner: Type: feature request | Status: patch Priority: normal | Milestone: Component: libraries/random | Version: 7.6.3 Resolution: | Keywords: fusion Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: #4218 -------------------------------------+------------------------------------ Comment (by ion1): Yes, I tested with {{{ main = do { gen <- newStdGen; mapM_ print (randoms gen) } }}} which resulted in the list data structure being optimized away entirely (along with the pattern match for the empty case in `mapM_`). I got around to doing some benchmarking after posting the patch and I seem unable to come up with code for which `randoms` fusion makes a difference in performance, though. Unless someone else thinks of something I didn’t, this might not be worth it. The `seq` fix for part of #4218 can be done independently. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8704#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler