<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;">How do I import Control.Monad.State?<br><br>I see this note in http://en.wikibooks.org/wiki/Haskell/Understanding_monads/State<br> <br>Note: in some package systems used for GHC, the Control.Monad.State module is in a separate package, usually indicated by MTL (Monad Transformer Library).<br><br>Michael<br><br><br>===============rand.hs ==============<br><br>import Control.Monad.State<br><br>type GeneratorState = State StdGen<br><br>rollDie :: GeneratorState Int<br>rollDie = do generator <- get<br> let( value, newGenerator ) = randomR (1,6) generator<br> put newGenerator<br> return
value<br><br>=======================<br><br>[michael@localhost ~]$ ghci rand<br>GHCi, version 6.12.1: http://www.haskell.org/ghc/ :? for help<br>Loading package ghc-prim ... linking ... done.<br>Loading package integer-gmp ... linking ... done.<br>Loading package base ... linking ... done.<br>Loading package ffi-1.0 ... linking ... done.<br><br>rand.hs:1:7:<br> Could not find module `Control.Monad.State':<br> Use -v to see a list of the files searched for.<br>Failed, modules loaded: none.<br>Prelude><br><br></td></tr></table><br>