Route.hs

site :: MVar SimState -> Snap ()
site sim = catch500 $
           ifTop (fileServe "static/index.html")
       <|> route [ ("vessel/speed/:speed", method PUT putSpeed sim)
                 , ("vessel",              method GET getSim sim)
                 ]
       <|> fileServe "static"

RouteWith.hs

-- putSpeed :: MVar SimState -> Snap ()
-- getSim :: MVar SimState -> Snap ()

site :: MVar SimState -> Snap ()
site sim = catch500 $
           ifTop (fileServe "static/index.html")
       <|> routeWith sim [ ("vessel/speed/:speed", method PUT <$> putSpeed)
                         , ("vessel",              method GET <$> getSim)
                         ]
       <|> fileServe "static"

routeWith :: a -> [(ByteString, a -> Snap ())] -> Snap ()
routeWith a = route . map f
  where
    f (r, h) = (r, h a)