[Haskell-cafe] Missing Symbol

Hi What symbol would you replace the "?" with: the identity function id x = x? My scanned copy of the Hutton book contains some rather interesting characters. In fact, the OCR program has placed a "." in place of most symbols - e.g. ->, <- ^, <=, \=, etc. Fortunately, I'm able to guess the correct operator in the majority of the cases. Cheers, Paul