In nhc98, Word is a type synonym, so class instance is not possible.

diff --git a/Text/Printf.hs b/Text/Printf.hs
index 4b11931..f14ac0e 100644 (file)
--- a/Text/Printf.hs
+++ b/Text/Printf.hs
@@ -147,8 +147,10 @@ instance PrintfArg Int32 where
 instance PrintfArg Int64 where
     toUPrintf = uInteger
 
+#ifndef __NHC__
 instance PrintfArg Word where
     toUPrintf = uInteger
+#endif
 
 instance PrintfArg Word8 where
     toUPrintf = uInteger