nav.elm

(=>) = (,)

navb : Address NavAction -> M.State -> List Html
navb addr model =
    [ div [class "navbar-spacer"] []
    , nav [class "navbar"]
        [ div [class "centered container" ]
            [
            ul [class "navbar-list"]
              [ li [class "navbar-item"] [
                    a [ classList ["active" => (model.page == "home"), "navbar-link" => True],
                        href "#home", onClick addr NavHome ]
                      [ text "Home" ]
                    ]
              , li [class "navbar-item"] [
                    a [ classList ["active" => (model.page == "find"), "navbar-link" => True],
                        href "#find", onClick addr NavFind ]
                      [ text "Find" ]
                    ]
              , li [class "navbar-item"] [
                    a [ classList ["active" => (model.page == "profile"), "navbar-link" => True],
                        href "#profile", onClick addr NavProfile ]
                      [ text "Profile" ]
                    ]
              , signInItem addr model
              ]
            ]
        ]
    ]

signInItem : Address NavAction -> M.State -> Html
signInItem addr model =
    let (name, url, act) = if isJust model.user
                        then ("Sign Out", "#signout", NavSignOut) else ("Sign In", "#signin", NavSignIn)
    in
      li [class "navbar-item"] [
            a [ classList ["active" => (model.page == "signin"), "navbar-link" => True],
                href url, onClick addr act ]
              [ text name ]
            ]

@alesch, (=>) = (,) is used to avoid extra parentheses and to ascribe meaning to the tuple. Without it, line 11 would have probably been:

a [ classList [("active", (model.page == "home")), ("navbar-link", True)],

making it less obvious that there is a semantic link between active and model.page == "home".

At least this is how I read it.