+#include <iostream>
+#include <cstdlib> // rand(), RAND_MAX
+#include "ginac.h"
+using namespace std;
+using namespace GiNaC;
+
+extern const ex
+sparse_tree(const symbol & x, const symbol & y, const symbol & z,
+ int level, bool trig = false, bool rational = true,
+ bool complex = false);
+extern const ex
+dense_univariate_poly(const symbol & x, unsigned degree);