From 777e8c945aa511b9af3b43eda1d994b99a03b8a2 Mon Sep 17 00:00:00 2001
From: Martin Clausen <martin.clausen@gmail.com>
Date: Fri, 18 Oct 2024 23:08:26 +0200
Subject: [PATCH] Update to use modern Haskell.

---
 .gitignore          |  1 +
 src/Observations.hs | 16 +++++++++-------
 src/XmlUtils.hs     |  4 ++--
 3 files changed, 12 insertions(+), 9 deletions(-)
 create mode 100644 .gitignore

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..4c61acd
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+dist-newstyle
\ No newline at end of file
diff --git a/src/Observations.hs b/src/Observations.hs
index 4fcdebf..4b380cd 100644
--- a/src/Observations.hs
+++ b/src/Observations.hs
@@ -74,14 +74,16 @@ unTEs (TEs x) = x
 instance Functor TimedEvents where
   fmap f (TEs tes) = TEs [ (t,f e) | (t,e) <- tes ]
 
-instance Monoid a => Monoid (TimedEvents a) where
-  mempty        = TEs []
-  mappend as bs =
-      fmap mappendMergeResult (mergeEvents as bs)
+instance Semigroup a => Semigroup (TimedEvents a) where
+  as <> bs =
+    fmap mappendMergeResult (mergeEvents as bs)
     where
-      mappendMergeResult (OnlyInLeft  a)   = a
-      mappendMergeResult (InBoth      a b) = a `mappend` b
-      mappendMergeResult (OnlyInRight   b) =             b
+      mappendMergeResult (OnlyInLeft a) = a
+      mappendMergeResult (InBoth a b) = a <> b
+      mappendMergeResult (OnlyInRight b) = b
+
+instance Semigroup a => Monoid (TimedEvents a) where
+  mempty = TEs []
 
   -- mconcat = --TODO: optimise mconcat to do more balanced merges
 
diff --git a/src/XmlUtils.hs b/src/XmlUtils.hs
index ac1815e..f9f00eb 100644
--- a/src/XmlUtils.hs
+++ b/src/XmlUtils.hs
@@ -10,13 +10,13 @@ import Text.XML.HaXml.Types (QName(..))
 import Text.XML.HaXml.XmlContent
 import Data.Time
 
-attrStr :: Monad m => QName -> Element t -> m String
+attrStr :: MonadFail m => QName -> Element t -> m String
 attrStr n (Elem _ as _) =
     case lookup n as of
       Nothing -> fail ("expected attribute " ++ localName n)
       Just av -> return (attr2str av)
 
-attrRead :: (Read b, Monad m) => QName -> Element t -> m b
+attrRead :: (Read b, MonadFail m) => QName -> Element t -> m b
 attrRead n e = do
     str <- attrStr n e
     case reads str of