#14349: Semigroup/Monoid instances for System.Exit.ExitCode -------------------------------------+------------------------------------- Reporter: neil.mayhew | Owner: (none) Type: feature request | Status: upstream Priority: low | Milestone: Component: libraries/base | Version: 8.2.1 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: | -------------------------------------+------------------------------------- Comment (by glguy): Having a Monoid instance doesn't seem like a good idea to me. The code above could be written more clearly using an explicitly named, locally defined operation: `combineExitCodes <$> mapM system commands`. Reusing `mconcat` isn't a win here. Having such a forced Monoid instance simply means that users will have to consult the documentation to find the instance declaration to determine what behavior it has. There isn't a natural meaning for `instance Monoid ExitCode` -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14349#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler