Controlling Eden


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Controlling Eden

Once you have done this, the screen will start displaying one of the micro-worlds, and eventually settle down into something like figure 1, below:

Figure An Eden display.

 

This shows the situation at the start of the bug's life. The line at the top is a reminder of some of the commands you can give Eden, to control the way it steps through the life. Do not try any of these until I say so, in section 1.5.

Below it are two lines showing various bits of status information: the bug's previous action; the direction it is facing; its position; what it is holding; the object, if any, it is standing next to; and the ``time''. Below that is the micro-world itself, the bug being indicated by a B.

The reason for having the status information is that the display is, because of the terminals we are forced to use, very crude. The bug may be in the same square as another object, but there is no way to display that in the diagram. Nor can we show what it is holding, or which way it is facing.

To appreciate how the control commands are used, you need to know how Eden runs a life. Essentially, Eden consists of two parts: a world-manager and a bug ``brain''. When you start a new life, these run in a series of cycles, each cycle being as follows:

1
The world-manager generates from the current world, an image on the bug's ``retina''. In some worlds, it may also generate various other perceptions, such as a ``smell'' indicating roughly where the food is.

2
It then activates the ``brain''. This ``thinks'' about the perceptions, and eventually comes back with a ``motor command''.

3
The world-manager works out how this action affects the bug and the rest of the world. It updates the world accordingly, displaying the changes on the screen.


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Next: Stepping through a life
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Jocelyn Paine
Thu Feb 15 00:11:34 GMT 1996