tasks a-s

Task/Queue-Definition/Oz/queue-definition.oz

@@ -0,0 +1,34 @@
+declare
+  fun {NewQueue}
+     Stream
+     WritePort = {Port.new Stream}
+     ReadPos = {NewCell Stream}
+  in
+     WritePort#ReadPos
+  end
+
+  proc {Push WritePort#_ Value}
+     {Port.send WritePort Value}
+  end
+
+  fun {Empty _#ReadPos}
+     %% the queue is empty if the value at the current
+     %% read position is not determined
+     {Not {IsDet @ReadPos}}
+  end
+
+  fun {Pop _#ReadPos}
+     %% blocks if empty
+     case @ReadPos of X|Xr then
+        ReadPos := Xr
+        X
+     end
+  end
+
+  Q = {NewQueue}
+in
+  {Show {Empty Q}}
+  {Push Q 42}
+  {Show {Empty Q}}
+  {Show {Pop Q}}
+  {Show {Empty Q}}