úκ$non-portable (uses Control.Monad.ST) experimentalmainland@eecs.harvard.eduThe 7 type class abstracts over the details of manipulating M references, allowing one to write code that uses references and can operate ) in either the ST monad or the IO monad. Create a new reference Read the value of a reference !Write a new value to a reference #Mutate the contents of a reference  ref-fd-0.1Control.Monad.RefMonadRefnewRefreadRefwriteRef modifyRef