#9536: Implement foldr/cons/build -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: Type: task | Status: new Priority: normal | Milestone: 7.8.4 Component: libraries/base | Version: 7.9 Keywords: fusion | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Easy (less than 1 | Type of failure: hour) | None/Unknown Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- There seem to be various issues with general `fold/cons` and even `cons/build` rules, but it seems pretty clear to me that the simple `fold/cons/build` rule is a good idea. It doesn't do much for nofib allocation, but it seems to improve some other analyses and speed several benchmarks up, including speeding up some things that other fusion changes slowed down. I say "seems to" because I never trust my timings much at all. {{{#!hs {-# RULES "foldr/cons/build" forall c n x (g::forall b. (a->b->b) -> b -> b) . foldr c n (x:build g) = c x (g c n) #-} }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9536 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler