From 7b8ea03caeba7c586d9e79a5ec4f522e8cd266da Mon Sep 17 00:00:00 2001
From: Max Ulidtko <ulidtko.gmail.com>
Date: Fri, 8 Sep 2023 18:13:44 +0200
Subject: [PATCH] Optimise instance Ord of SourcePos

See issue #171.

Co-Authored-By: Matt Parsons <parsonsmatt@gmail.com>
---
 src/Text/Parsec/Pos.hs | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/Text/Parsec/Pos.hs b/src/Text/Parsec/Pos.hs
index 02a7b213..a1db74bd 100644
--- a/src/Text/Parsec/Pos.hs
+++ b/src/Text/Parsec/Pos.hs
@@ -41,7 +41,12 @@ type Column     = Int
 -- 'Ord' class.
 
 data SourcePos  = SourcePos SourceName !Line !Column
-    deriving ( Eq, Ord, Data, Typeable)
+    deriving (Eq, Data, Typeable)
+
+-- | The ordering compares first by line, column, then by sourcename.
+instance Ord SourcePos where
+  compare (SourcePos snA lnA colA) (SourcePos snB lnB colB)
+    = lnA `compare` lnB <> colA `compare` colB <> snA `compare` snB
 
 -- | Create a new 'SourcePos' with the given source name,
 -- line number and column number.