#9949: zipWith too strict in second argument in GHC-7.10.0 -------------------------------------+------------------------------------- Reporter: Lemming | Owner: ekmett Type: bug | Status: new Priority: highest | Milestone: Component: libraries/base | Version: 7.10.1-rc1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: None/Unknown | Unknown/Multiple Blocked By: | Test Case: Related Tickets: #9495 | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by tibbe): I think we should * revert the change, * remove the rule, and * document the intended strictness. The lack of the latter has proved to be problematic elsewhere (e.g. `findWithDefault` in containers.) Without documenting the strictness properties users can't really assume anything about the strictness of functions. Not even a "lazy unless otherwise specified" assumption is warranted, as functions are rarely maximally lazy unless particular care is taken (see e.g. https://www.haskell.org/haskellwiki/Maintaining_laziness). -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9949#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler