Object Tree

The object tree is the hierarchy of objects in the Hugo world that you create. The object tree is the internal representation of the relationships between the various objects in the game.

The Branches

The first object that is defined (in the Hugo standard library) is the nothing object. This is the root of the object tree and all the other objects are children of this one.

Let’s take a look at a sample. Let’s say you’ve created a room called kitchen with a table and counter located inside it. On the table are a plate and fork, and on the counter some eggs. The object tree may be something like the following:

The parent of the kitchen object (room) is the nothing object. The children of the kitchen are table, counter and the player character. The table object has two children (the plate and fork) and the counter has one child (the eggs).

Climbing Around

There are a number of built-in functions that can be used to read the object tree:

Function	Definition
parent()	Returns the parent of the object
sibling()	Returns the next sibling
child()	Returns the child of the object
youngest()	Returns the youngest child of the object
elder()	Returns the older sibling (the next object to the left on the object tree graph)
eldest()	Returns the oldest child of the object (same as child())
younger()	Returns the younger sibling (the next object to the right on the object tree graph); same as sibling()
children()	Returns the number of children the object has

Each of these functions takes a single object as an argument. If we were to use the functions on the above table, they would return the following:

Function	Returns
parent(table)	kitchen
sibling(table) younger(table)	counter
child(counter) eldest(counter)	eggs
youngest(kitchen)	player
elder(table)	0 (nothing)
elder(plate)	0 (nothing)
children(kitchen)	3 (number of objects that are directly below kitchen)
children(eggs)	0

Now, let’s take a look at the table if the player types the following commands in the game

>Get eggs. Put eggs on the plate.

The object tree will now look like this:

As you can see, the parent of eggs has become the plate object.

When creating an object, use the in <object> command to place it in a certain part of the tree.

object table "kitchen table"
{
    noun "table"
    adjectives "brown", "kitchen", "small"
    in kitchen

    long_desc
    {
      ! rest of code
    }
}

If you don’t specify where in the tree an object resides, it will default to nothing.

The nearby property

You can also use the command nearby or nearby <object> to give object the same parent as <object>, or if <object> is not specified, the same parent as the last-defined object.

object eraser "chalkboard eraser"
{
   article "the"
   adjective "chalkboard"
   noun "eraser"
   nearby chalkboard ! starts in same room as chalkboard object
}

object desk "desk"
{
   article "the"
   noun "desk"
   nearby   ! is in the same room as last-defined object
}

Falling Off (AKA Rookie Mistakes)

Generally, it’s a lot safer to check up the object tree instead of down. if child(object) = other_object will only work when other_object is the oldest child in the tree.

On the flip side of that coin, though, are statements like if parent(object) = location. If you’re checking on the player, it’ll be false if the player is in a vehicle or on a platform (like a chair). If you’re checking for an object, it’ll be false if it’s on a platform or in a container or in the player’s possession, even. This might be obvious right now- as you’ve just read this page- but it’s easy to forget!

To get around these issues, you’ll want to use routines like Contains, which checks to see if an object is a child or grandchild of another object, or FindObject, which checks to see if an object is in a specific location. It even returns a special value if it can be seen but can’t be reached (like in a closed, transparent container).

That’s it! Go hug an object tree today!