From 7a0e274b20347bc51e7c43680ba4b5c3e5cefe0f Mon Sep 17 00:00:00 2001
From: Stephen Diehl <stephen.m.diehl@gmail.com>
Date: Mon, 10 Oct 2016 11:13:26 +0100
Subject: [PATCH] note and hush for #22

---
 protolude.cabal   |  1 +
 src/Exceptions.hs | 28 ++++++++++++++++++++++++++++
 src/Protolude.hs  |  1 +
 3 files changed, 30 insertions(+)
 create mode 100644 src/Exceptions.hs

diff --git a/protolude.cabal b/protolude.cabal
index 6af9af06f..a0c5fcc05 100644
--- a/protolude.cabal
+++ b/protolude.cabal
@@ -46,6 +46,7 @@ library
     Functor
     Semiring
     Bifunctor
+    Exceptions
     Panic
 
   other-modules:
diff --git a/src/Exceptions.hs b/src/Exceptions.hs
new file mode 100644
index 000000000..ec77b1f43
--- /dev/null
+++ b/src/Exceptions.hs
@@ -0,0 +1,28 @@
+{-# LANGUAGE Trustworthy #-}
+{-# LANGUAGE NoImplicitPrelude #-}
+
+module Exceptions (
+  hush,
+  note,
+  tryIO,
+) where
+
+import Base (IO)
+import Data.Function ((.))
+import Control.Monad.Trans (liftIO)
+import Control.Monad.IO.Class (MonadIO)
+import Control.Monad.Except (ExceptT(..), MonadError, throwError)
+import Control.Exception as Exception
+import Control.Applicative
+import Data.Maybe (Maybe, maybe)
+import Data.Either (Either(..))
+
+hush :: Alternative m => Either e a -> m a
+hush (Left _)  = empty
+hush (Right x) = pure x
+
+note :: (MonadError e m) => e -> Maybe a -> m a
+note err = maybe (throwError err) pure
+
+tryIO :: MonadIO m => IO a -> ExceptT IOException m a
+tryIO = ExceptT . liftIO . Exception.try
diff --git a/src/Protolude.hs b/src/Protolude.hs
index f2bd9d2e3..32b8d786f 100644
--- a/src/Protolude.hs
+++ b/src/Protolude.hs
@@ -35,6 +35,7 @@ import Either as X
 import Applicative as X
 import Conv as X
 import Panic as X
+import Exceptions as X
 
 import Base as Base hiding (
     putStr           -- Overriden by Show.putStr