That works, but is probably not what you want. You can use the lex function to parse identifiers not enclosed in quotes:

instance Read Mark where readsPrec _ str = [(Mark x, t') | ("mark",t) <- lex str, (x,t') <- reads t

I played a bit around with lex function and it seems that under certain circumstances it doesn't read the string of token properly For e.g. -- IP address *Mark> lex "192.168.0.1" [("192.168",".0.1")] -- digit + char Also lex "8021p" output is *Mark> lex "8021p" [("8021","p")] Is there any other lex variant available? Or should I switch to using Parsec library, in that case, will I still be able to use it with Read instances? If so, how? Anurag