#8532: Hyperbolic arc cosine fails on (-1) :: Complex r. -------------------------------------+------------------------------------- Reporter: leftaroundabout | Owner: Type: bug | Status: new Priority: low | Milestone: Component: libraries/base | Version: 7.6.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: Incorrect result | Difficulty: Easy (less than 1 at runtime | hour) Test Case: acosh(-1) :: | Blocked By: Complex Double | Related Tickets: Blocking: | -------------------------------------+------------------------------------- Changes (by carter): * cc: hvr, ekmett (added) Comment: hrmm, so one issue with complex functions in general is that there (is always) a "branch cut" http://mathworld.wolfram.com/BranchCut.html http://en.wikipedia.org/wiki/Branch_point http://math.stackexchange.com/questions/245579/how-does-a-branch-cut- define-a-branch are some of the first few decent hits on google for this topic. So do we standardize on the "common" branch cut choice? I'm not sure. If we don't enrich the complex function apis to be somehow parameterized by the branchcut choice, thats probably the "right" thing to do. ("right" being of course not quite the right term) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8532#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler