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-rw-r--r--compiler/utils/MonadUtils.hs18
1 files changed, 18 insertions, 0 deletions
diff --git a/compiler/utils/MonadUtils.hs b/compiler/utils/MonadUtils.hs
index 9b364aebb7..5e01a222b2 100644
--- a/compiler/utils/MonadUtils.hs
+++ b/compiler/utils/MonadUtils.hs
@@ -8,6 +8,8 @@ module MonadUtils
, MonadFix(..)
, MonadIO(..)
+
+ , ID, runID
, liftIO1, liftIO2, liftIO3, liftIO4
@@ -22,6 +24,8 @@ module MonadUtils
, maybeMapM
) where
+import Outputable
+
----------------------------------------------------------------------------------------
-- Detection of available libraries
----------------------------------------------------------------------------------------
@@ -43,6 +47,20 @@ import Control.Monad
import Control.Monad.Fix
----------------------------------------------------------------------------------------
+-- The ID monad
+----------------------------------------------------------------------------------------
+
+newtype ID a = ID a
+instance Monad ID where
+ return x = ID x
+ (ID x) >>= f = f x
+ _ >> y = y
+ fail s = panic s
+
+runID :: ID a -> a
+runID (ID x) = x
+
+----------------------------------------------------------------------------------------
-- MTL
----------------------------------------------------------------------------------------