add examples

examples/woods/common.py

@@ -0,0 +1,58 @@
+# Helpers
+def state_of(od, animal):
+    return od.get_source(od.get_incoming(animal, "of")[0])
+def animal_of(od, state):
+    return od.get_target(od.get_outgoing(state, "of")[0])
+def get_time(od):
+    _, clock = od.get_all_instances("Clock")[0]
+    return clock, od.get_slot_value(clock, "time")
+
+
+# Render our run-time state to a string
+def render_woods(od):
+    txt = ""
+    _, time = get_time(od)
+    txt += f"T = {time}.\n"
+    txt += "Bears:\n"
+    def render_attacking(animal_state):
+        attacking = od.get_outgoing(animal_state, "attacking")
+        if len(attacking) == 1:
+            whom_state = od.get_target(attacking[0])
+            whom_name = od.get_name(animal_of(od, whom_state))
+            return f" attacking {whom_name}"
+        else:
+            return ""
+    def render_dead(animal_state):
+        return 'dead' if od.get_slot_value(animal_state, 'dead') else 'alive'
+    for _, bear_state in od.get_all_instances("BearState"):
+        bear = animal_of(od, bear_state)
+        hunger = od.get_slot_value(bear_state, "hunger")
+        txt += f"  🐻 {od.get_name(bear)} (hunger: {hunger}, {render_dead(bear_state)}) {render_attacking(bear_state)}\n"
+    txt += "Men:\n"
+    for _, man_state in od.get_all_instances("ManState"):
+        man = animal_of(od, man_state)
+        attacked_by = od.get_incoming(man_state, "attacking")
+        if len(attacked_by) == 1:
+            whom_state = od.get_source(attacked_by[0])
+            whom_name = od.get_name(animal_of(od, whom_state))
+            being_attacked = f" being attacked by {whom_name}"
+        else:
+            being_attacked = ""
+        txt += f"  👨 {od.get_name(man)} ({render_dead(man_state)}) {render_attacking(man_state)}{being_attacked}\n"
+    return txt
+
+
+# When should simulation stop?
+def termination_condition(od):
+    _, time = get_time(od)
+    if time >= 10:
+        return "Took too long"
+
+    # End simulation when 2 animals are dead
+    who_is_dead = []
+    for _, animal_state in od.get_all_instances("AnimalState"):
+        if od.get_slot_value(animal_state, "dead"):
+            animal_name = od.get_name(animal_of(od, animal_state))
+            who_is_dead.append(animal_name)
+    if len(who_is_dead) >= 2:
+        return f"{' and '.join(who_is_dead)} are dead"