From 9911c1f1358df059c6694c31a5b2452a35c8d748 Mon Sep 17 00:00:00 2001
From: simonpj <unknown>
Date: Wed, 28 Aug 2002 14:30:12 +0000
Subject: [PATCH] [project @ 2002-08-28 14:30:12 by simonpj] Fix a lexing bug:
 "\SOH" could mean "\SO" followed by "H" or "\SOH".  The
 Report specifies the latter.

	MERGE TO STABLE
---
 Text/Read/Lex.hs |   11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/Text/Read/Lex.hs b/Text/Read/Lex.hs
index 01ca6ac..e9b7635 100644
--- a/Text/Read/Lex.hs
+++ b/Text/Read/Lex.hs
@@ -217,8 +217,14 @@ lexChar =
 
   lexAscii =
     do choice
-         [ string "NUL" >> return '\NUL'
-         , string "SOH" >> return '\SOH'
+         [ do { string "SO" ; s <- look; 
+		case s of
+		  'H' : _ -> do { get ; return '\SOH' }
+		  other   -> return '\SO' 
+	      }
+		-- \SO and \SOH need maximal-munch treatment
+		-- See the Haskell report Sect 2.6
+         , string "NUL" >> return '\NUL'
          , string "STX" >> return '\STX'
          , string "ETX" >> return '\ETX'
          , string "EOT" >> return '\EOT'
@@ -231,7 +237,6 @@ lexChar =
          , string "VT"  >> return '\VT'
          , string "FF"  >> return '\FF'
          , string "CR"  >> return '\CR'
-         , string "SO"  >> return '\SO'
          , string "SI"  >> return '\SI'
          , string "DLE" >> return '\DLE'
          , string "DC1" >> return '\DC1'
-- 
1.7.10.4