apply rule to multiple facts?

[Xuan Wu]

Hi all,

I'm still learning and trying to simulate an ecosystem, with multiple lives aging as time flies. Seems one rule only applies to the newest fact, and I can't get all lives aging together. As a test case:

```

(deftemplate human
  (slot id)
  (slot age))

(defrule time_flies
  ?h <- (human (id ?id) (age ?age))
  =>
  (modify ?h (age (+ ?age 1))))

```

and two facts:

(assert (human (id 0) (age 0)))

(assert (human (id 1) (age 0)))

When running I got fact 1 and 2, with only 2 aging by itself. My goal is to see 1 and 2 aging hopefully at the same speed.

Any suggestion is appreciated.

[Ryan Johnston]

In CLIPS, the order in which things execute is not guaranteed. Thus, you must build your rules in a way that explicitly describes that, once one human ages, it should not age again until all other humans have aged.

One way you could achieve this is by adding a test such that the rule only triggers for humans with no other human facts are younger than it. Something like (not (human (age ?a&:(< ?a ?age)))). This would give other human facts a chance to "catch up" to the human facts that have already aged.

This works for your current scenario in which all humans start at the same age. If you will have humans of different ages, you'll need to track something like "number of times a human fact has aged" along with a humans overall age.

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[Xuan Wu]

Thanks a lot! The solution works. For now I chose to keep the time of birth instead of refreshing age, just to avoid the complexity of adding tracking. Nevertheless thanks for the suggestion.