Section: Selection

    After looking:
        let N be indexed text;
        let N be "[selection of the visible doors conforming to the description open visible doors is-are]";
        say "[N in sentence case] open.".

to produce such phrases as "Neither of them is open.", "All three of them are open.", "The black door is open.", and so on. It is necessary to give both descriptions in full and not to take a shortcut such as "selection of the visible doors which are open". It is the author's responsibility to ensure that the subset description is really a subset of the superset description. (It would be possible to check for this within Inform, but at some runtime performance cost if the sets are complicated; so we preferred the speedier option.)