Initial data commit

Task/Stack/Sather/stack-1.sa

@@ -0,0 +1,33 @@
+class STACK{T} is
+  private attr stack :LLIST{T};
+
+  create:SAME is
+    res ::= new;
+    res.stack := #LLIST{T};
+    return res;
+  end;
+
+  push(elt: T) is
+    stack.insert_front(elt);
+  end;
+
+  pop: T is
+    if ~stack.is_empty then
+      stack.rewind;
+      r ::= stack.current;
+      stack.delete;
+      return r;
+    else
+      raise "stack empty!\n";
+    end;
+  end;
+
+  top: T is
+    stack.rewind;
+    return stack.current;
+  end;
+
+  is_empty: BOOL is
+    return stack.is_empty;
+  end;
+end;