[I6] Initial property (when used for rooms)

Authoring Inform 6
1

I was surprised to discover in Appendix A2 of the DM4 a note about the initial property:

For rooms Printed or run when the room is arrived in, either by ordinary movement or by PlayerTo.

I gave this a quick test, but I noticed that whatever is in initial is presented every time the room in question is entered, as opposed to only the first time (as might be naively expected as a parallel to its function for non-room objects).

Looking at the Standard Library (6.12.4), the behavior is regulated by a routine called NoteArrival():

[ NoteArrival descin;
    if (location == thedark) { lastdesc = thedark; return; }
    if (location ~= lastdesc) {
        if (location.initial ~= 0) PrintOrRun(location, initial);
        descin = location;
        NewRoom();
        lastdesc = descin;
    }
];

It’s not difficult to change NoteArrival() so that it only prints/runs the contents of a room on the first visit:

[ NoteArrival descin;
    if (location == thedark) { lastdesc = thedark; return; }
    if (location ~= lastdesc) {
        if (location.initial ~= nothing && location hasnt visited) PrintOrRun(location, initial); ! THIS LINE MODIFIED
        descin = location;
        NewRoom();
        lastdesc = descin;
    }
];

DM4 doesn’t have a single example of an initial property for a room object in any example code. (I just checked.) The phrase “initial for a room” is mentioned fleetingly in the table of contents summary for section 21; in that section the relevant discussion seems to be limited to rule 4a in the Standard Library’s rules for what’s printed upon a change of location for the player object (pages 154-155, DM4 §21: Starting, moving, changing and killing the player). I’m not sure how many people even know that this is a feature.

There might be too high of a risk of backwards compatibility issues to consider a change in the Standard Library, even though making this change would create some conceptual consistency to the function of initial across both “new” objects (~moved) and “new” rooms (~visited). And it would simplify the beginner author’s task of trying to make the first arrival in a room a little special to the player (which I think I’ve seen several posts about in the past, though probably some were for I7).

For the latter reason, I thought it would be worth posting the idea here for posterity.

On a related note, another fun fact: The inside_description property also has a special function for rooms – it is printed or run after the normal description property, so it looks like a coda to the room description. Interestingly, this happens even if in “superbrief” mode.

2

When I was writing games in I6, I used initial heavily in its current meaning.

I note that with the current meaning, it’s easy to write code that only runs the first time you visit a room. (Write an initial routine that checks visited.) If you change its meaning to that, it would become difficult to write code that runs every time the room is entered.

3

Good point!

4

Do what zarf said. This gives you the flexibility of doing something the first time you enter a room or every time you enter a room and different rooms can be treated differently.

5

The current arrangement allows you to have different text shown on entering the room and on look, which can be useful.