[xmonad] list of visible workspaces

How do you get a list of visible workspaces (only those workspaces that are displayed on the monitors)? Currently I get the entire list of workspaces in my xmonad config with (XMonad.workspaces conf). It looks like this command returns a list of strings, each of which denote a workspace (i.e. ["1", "2"... ] ). But not sure how to get a list of only those which are visible (I could also probably work with a list of hidden workspaces). Sorry, my Haskell is weak and I do not understand how to use the documentation here: http://xmonad.org/xmonad-docs/xmonad/XMonad-StackSet.html Thanks!