[Haskell-cafe] Hash table constructors return table in IO Monad. Why?

[Stephen Tetley]

The hashtable needs to be been created in IO, after that, think of the
'hashtable' as a analogous to a file handle. You have to pass it
around to do anything with it - but the only things you can do with it
are in IO.

(That's why no-one really likes it, of course...)