#13097: Num a => Num (Down a) -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: libraries/base | Version: 8.0.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Description changed by Iceland_jack: @@ -19,2 +19,2 @@ - `MonadFix`, ... I don't know that they would ever get but it wouldn't be - much trouble copying `Identity`, `Dual` instances. + `MonadFix`, ... I don't know that they would see use but we can use + `Identity`, `Dual` instances. New description: There are many missing instances for `Down`, I happened to need `Num (Down _)`. It can be derived with GND: {{{#!hs newtype Down a = Down a deriving (Eq, Show, Read, Num) }}} which let's us write {{{#!hs
(<) 10 20 True
(<) @(Down _) 10 20 False }}}
We can of course add instances for `Functor`, `Applicative`, `Monad`, `MonadFix`, ... I don't know that they would see use but we can use `Identity`, `Dual` instances. ---- With #12363 {{{#!hs
10 < @(Down _) 20 False }}}
with #12363 + #12465 {{{#!hs
10 < @Down{} 20 False }}}
-- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13097#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler