#8012: Warn when using Enum instance for Float or Double -----------------------------+---------------------------------------------- Reporter: gidyn | Owner: Type: feature request | Status: new Priority: normal | Component: Compiler Version: 7.6.3 | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: None/Unknown | Blockedby: Blocking: | Related: -----------------------------+---------------------------------------------- The Enum instances for Float and Double have dubious semantics which cause endless confusion, e.g. [http://stackoverflow.com/questions/13203471/the-math- behind-1-0999999999999999-in-haskell], [http://stackoverflow.com/questions/9810002/floating-point-list- generator], [http://stackoverflow.com/questions/7290438/haskell-ranges-and-floats], [http://stackoverflow.com/questions/10328435/how-to-solve-floating-point- number-getting-wrong-in-list-haskell], and many more. It is therefore proposed that the usage of an Enum instance for Float or Double generate a compiler warning, such as "The Enum instance for Float is subject to rounding errors". A discussion of this on [http://haskell.1045720.n5.nabble.com/Proposal- Warn-when-using-Enum-instance-of-Float-or-Double-td5731620.html the libraries list] suggested that such a warning would be desired, although the discussion mostly focused on whether the libraries list is an appropriate place for this discussion. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/8012 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler