Hi folks, I'm using Parsec to parse a stream of tokens. The token primitive takes, among other arguments, a function to print tokens. However, this function is not always applied. Try the code below: --------- import Text.ParserCombinators.Parsec import Text.ParserCombinators.Parsec.Pos(newPos) mytoken :: (Eq t, Show t) => t -> GenParser (SourcePos,t) () t mytoken x = token showTok posFromTok testTok where showTok (pos,t) = "<" ++ show t ++ ">" posFromTok (pos,t) = pos testTok (pos,t) = if (x == t) then Just t else Nothing main = do putStrLn "" case parse the123Parser "" [(newPos "" 1 n, n) | n <- [1,2,3,4]] of (Left err) -> putStrLn (show err) (Right _) -> putStrLn "parsed correctly" putStrLn "" case parse the123Parser "" [(newPos "" 1 n, n) | n <- [1,3,4]] of (Left err) -> putStrLn (show err) (Right _) -> putStrLn "parsed correctly" the123Parser = do mytoken 1 mytoken 2 mytoken 3 eof return 123 ------- The output I get looks like this: (line 1, column 4): unexpected [((line 1, column 4),4)] expecting end of input (line 1, column 3): unexpected <3> In the second parse case, it correctly uses my showTok function to show the token. But in the first case, it just uses the regular show method. I guess that's because the eof parser doesn't know anything about how to show the token it sees. Any ideas on how I can get the error message in the first case to look more like the second case? Thanks, Lyle