From 9b65d9650404d8b7202fc63ba23554d734589f20 Mon Sep 17 00:00:00 2001 From: Joey Hess Date: Mon, 31 Mar 2014 10:36:45 -0400 Subject: monoid --- Propellor/Types.hs | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) (limited to 'Propellor/Types.hs') diff --git a/Propellor/Types.hs b/Propellor/Types.hs index 70ad8f9b..ec472ffe 100644 --- a/Propellor/Types.hs +++ b/Propellor/Types.hs @@ -1,5 +1,7 @@ module Propellor.Types where +import Data.Monoid + type HostName = String type UserName = String @@ -14,9 +16,11 @@ type Desc = String data Result = NoChange | MadeChange | FailedChange deriving (Show, Eq) -combineResult :: Result -> Result -> Result -combineResult FailedChange _ = FailedChange -combineResult _ FailedChange = FailedChange -combineResult MadeChange _ = MadeChange -combineResult _ MadeChange = MadeChange -combineResult NoChange NoChange = NoChange +instance Monoid Result where + mempty = NoChange + + mappend FailedChange _ = FailedChange + mappend _ FailedChange = FailedChange + mappend MadeChange _ = MadeChange + mappend _ MadeChange = MadeChange + mappend NoChange NoChange = NoChange -- cgit v1.2.3