Section - Exits

[This routine is lifted straight from the example in the Inform 7 docs.]

Understand "exits" as listing exits. Listing exits is an action out of world applying to nothing.

Definition: a direction (called thataway) is viable if the room thataway from the location is a room.

Carry out listing exits (this is the Keyword Interface carry out listing exits rule):
    let count of exits be the number of viable directions;
    if the count of exits is 0, show KI message for no-available-exits;
    otherwise show KI message for show-available-exits instead.