White space in "do notation" is no longer supported by GHC but I had to guess it the hard way seeing my solutions to Hutton's book and then his own code produce "Parse error" and irritating hint "Possibly caused by a missing 'do'?". So, Hutton 2ed is outdated, Haskell Platform is dropped exhausted then perhaps GHC should have a TV station?
Fun is best when it can be shared.