From: Bas van Dijk <v.dijk.bas@gmail.com>
Date: Sun, 16 May 2010 16:06:51 +0000 (+0000)
Subject: Moved MonadPlus instance for STM from Control.Monad.STM to GHC.Conc to avoid an orpha... 
X-Git-Url: http://git.megacz.com/?a=commitdiff_plain;h=79ea2dac8f58dace80758c734354258868a1d0a0;p=ghc-base.git

Moved MonadPlus instance for STM from Control.Monad.STM to GHC.Conc to avoid an orphaned instance
---

diff --git a/GHC/Conc.lhs b/GHC/Conc.lhs
index 715e569..c1b2107 100644
--- a/GHC/Conc.lhs
+++ b/GHC/Conc.lhs
@@ -476,6 +476,10 @@ thenSTM (STM m) k = STM ( \s ->
 returnSTM :: a -> STM a
 returnSTM x = STM (\s -> (# s, x #))
 
+instance MonadPlus STM where
+  mzero = retry
+  mplus = orElse
+
 -- | Unsafely performs IO in the STM monad.  Beware: this is a highly
 -- dangerous thing to do.  
 --