[Haskell-beginners] defining functions in ghci

This messes me up: $ ghci GHCi, version 6.8.2: http://www.haskell.org/ghc/ :? for help double x =Loading package base ... linking ... done. Prelude> double x = x + x <interactive>:1:9: parse error on input `=' Why does that happen? -- Joe Van Dyk http://fixieconsulting.com