#13280: Consider deriving more Foldable methods -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: dfeuer Type: task | Status: new Priority: normal | Milestone: 8.2.1 Component: Compiler | Version: 8.0.1 Resolution: | Keywords: deriving-perf Operating System: Unknown/Multiple | Architecture: Type of failure: Runtime | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by dfeuer): Note about `length`, so I don't forget: For the nested case, {{{#!hs Con ... f (g a) ... }}} the way to make sure we never do worse than the default `length` definition (assuming the recursively called `length` is good) is to use {{{#!hs length (Con ... fga ...) = ... + foldl' (\acc x -> acc + length x) 0 fga + ... }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13280#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler