#9238: Negative zero broken -------------------------------------+------------------------------------- Reporter: augustss | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Resolution: | Keywords: Operating System: | Architecture: Unknown/Multiple Unknown/Multiple | Difficulty: Unknown Type of failure: Incorrect | Blocked By: result at runtime | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by simonpj): I can tell you exactly where it's created: line 2107 of `Simplify.lhs` (in today's HEAD), in function `simplAlt`. However I'm suspicious of adding a special case for float/double here. Rather, I think we should prohibit using Core-language `case` expressions to scrutinise float/double, so that `case` (in Core) behaves in a simple, predictable way. Rather I think we should probably generate {{{ case eqDouble# ds1 0.0## of True -> ... False -> ... }}} (or, rather, today's unboxed-boolean version). Now the magic is confined to how `eqDouble#` is implemented, which is the proper place for it. Now Haskell source code does allow case expressions over floats, but that's just a question of fixing the desugarer. Does that make sense? Does anyone feel like taking this on? Simon -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9238#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler