Author:halw

Date:2011-04-08T23:03:48.000000Z


git-svn-id: https://svn.eiffel.com/eiffel-org/trunk@869 abb3cda0-5349-4a8f-a601-0c33ac3a8c38

documentation/current/solutions/concurrent-computing/concurrent-eiffel-scoop/scoop-examples/faneuil-hall.wiki

@@ -13,6 +13,33 @@ The scenario in the Faneuil Hall example involves a number of immigrants waiting
 
 =Highlights=
 
+The primary actors here are the immigrants, the judge, and the spectators, model by classes <code>IMMIGRANT</code>, <code>JUDGE</code>, and <code>SPECTATOR</code>, respectively. Some of the common behavior of these classes is abstracted into a deferred parent class, <code>ACTOR</code>. In addition to the actor classes, there is a class <code>HALL</code> that represents Faneuil Hall itself, and a root class that sets everything up and starts the processing. There is only one judge, but there will be a maximum combined number of immigrants and spectators. The specific number of immigrants versus spectators varies at random from one execution to the next.  
+
+Although not really considered an actor here (at least not a descendant of class <code>ACTOR</code>) the class <code>HALL</code> plays a critical role in managing the concurrent actions of the immigrants, spectators, and the judge. <code>HALL</code> includes many status queries which, when used in preconditions in features of the other actors, constitute [[Concurrent Eiffel with SCOOP#Preconditions|uncontrolled precondition clauses]] which when false will cause the calling processor to wait until the condition becomes true. For example, consider the following status query from class <code>HALL</code>:
+
+<code>
+    immigrants_ready: BOOLEAN
+            -- Are immigrants ready?
+        do
+            Result := immigrant_count = ready_immigrant_count
+        end
+</code>
+
+This query is used by the <code>JUDGE</code> when preparing to sit and administer oaths to the immigrants:
+
+<code>
+    take_place (a_hall: separate HALL)
+            -- Prepare to confirm.
+        require
+            immigrants_ready: a_hall.immigrants_ready
+        do
+            print (out + " taking place%N")
+            a_hall.sit_judge
+        end
+</code>
+
+The judge will take his place only when all the immigrants present have checked in and are ready to take the oath.
+