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Bryan O'Sullivan committed 086bd0a

Improve error messages.

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  • Parent commits df2d4c5

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Data/Text/Lazy/Read.hs

 {-# SPECIALIZE decimal :: Reader Int #-}
 {-# SPECIALIZE decimal :: Reader Integer #-}
 decimal txt
-    | T.null h  = Left "no digits in input"
+    | T.null h  = Left "input does not start with a digit"
     | otherwise = Right (T.foldl' go 0 h, t)
   where (h,t)  = T.spanBy isDigit txt
         go n d = (n * 10 + fromIntegral (digitToInt d))
 {-# SPECIALIZE hex :: Reader Int #-}
 {-# SPECIALIZE hex :: Reader Integer #-}
 hex txt
-    | T.null h  = Left "no digits in input"
+    | T.null h  = Left "input does not start with a hexadecimal digit"
     | otherwise = Right (T.foldl' go 0 h, t)
   where (h,t)  = T.spanBy isHexDigit txt
         go n d = (n * 16 + fromIntegral (hexDigitToInt d))
 char :: (Char -> Bool) -> Parser Char
 char p = P $ \t -> case T.uncons t of
                      Just (c,t') | p c -> Right (c,t')
-                     _                 -> Left "char"
+                     _                 -> Left "character does not match"
 
 data T = T !Integer !Int