#9548: Numerical type system problem -------------------------------------+------------------------------------- Reporter: vxanica | Owner: Type: feature | Status: new request | Milestone: Priority: normal | Version: 7.8.3 Component: | Keywords: Number libraries/base | Architecture: Unknown/Multiple Resolution: | Difficulty: Unknown Operating System: | Blocked By: Unknown/Multiple | Related Tickets: Type of failure: | None/Unknown | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by ekmett): All numbers do not have a decidable notion of equality. {{{ instance Num b => Num (a -> b) }}} is the most common example, but computable reals and purely symbolic numeric types are other counter examples. GHC 7.4 deliberately made a breaking change away from the Haskell 98 standard to avoid forcing users to lie about equalities that couldn't exist. Going back on that decision would be a mistake. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9548#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler