June 2018 Update

Task/Queue-Definition/Elena/queue-definition.elena

@@ -0,0 +1,62 @@
+import extensions.
+
+template queue :: type
+{
+    array<type> theArray.
+    int         theTop.
+    int         theTale.
+
+    explicit
+    [
+        theArray := type<>(8).
+        theTop := 0.
+        theTale := 0.
+    ]
+
+    bool empty
+        = theTop == theTale.
+
+    push type:anObject
+    [
+        if (theTale > theArray length)
+        [
+            theArray := theArray reallocate(theTale).
+        ].
+
+        theArray[theTale] := anObject.
+
+        theTale += 1.
+    ]
+
+    type pop
+    [
+        if (theTale == theTop)
+            [ InvalidOperationException new:"Queue is empty"; raise ].
+
+        type item := theArray[theTop].
+
+        theTop += 1.
+
+        ^ item
+    ]
+}
+
+program =
+[
+    queue<int> q := queue<int>().
+    q push(1).
+    q push(2).
+    q push(3).
+    console printLine(q pop).
+    console printLine(q pop).
+    console printLine(q pop).
+    console printLine("a queue is ", q empty; iif("empty","not empty")).
+    console print("Trying to pop:").
+    try(q pop)
+    {
+        on(Exception e)
+        [
+            console printLine(e message)
+        ]
+    }
+].