[Haskell-cafe] Question on `runState'

In this excerpt from the `StateArrow' page: runState :: Arrowhttp://hackage.haskell.org/packages/archive/base/4.2.0.2/doc/html/Control-Ar...a => StateArrowhttp://hackage.haskell.org/packages/archive/arrows/0.4.1.2/doc/html/Control-...s a *e* b -> a (e, s) (b, s)Sourcehttp://hackage.haskell.org/packages/archive/arrows/0.4.1.2/doc/html/src/Cont... what's the significance of having written "StateArrow s a *e* b", instead of "StateArrow s a b c"? Thanks, -db