Improve heur_gcd() so it can handle rational polynomials, and add a test case.

[ginac.git] / check / heur_gcd_bug.cpp

diff --git a/check/heur_gcd_bug.cpp b/check/heur_gcd_bug.cpp
new file mode 100644 (file)
index 0000000..6fa8060
--- /dev/null
+++ b/check/heur_gcd_bug.cpp
@@ -0,0 +1,39 @@
+/**
+ * @file heur_gcd_oops.cpp Check for a bug in heur_gcd().
+ *
+ * heur_gcd() did not check if the arguments are integer polynomials
+ * (and did not convert them to integer polynomials), which lead to
+ * endless loop or (even worse) wrong result.
+ */
+#include <iostream>
+#include "ginac.h"
+using namespace GiNaC;
+using namespace std;
+
+int main(int argc, char** argv)
+{
+       cout << "checking if heur_gcd() can cope with rational polynomials. ";
+       const symbol x("x");
+       const ex _ex1(1);
+       ex a1 = x + numeric(5, 4);
+       ex a2 = x + numeric(5, 2);
+       ex b =  pow(x, 2) + numeric(15, 4)*x + numeric(25, 8);
+       // note: both a1 and a2 divide b
+       
+       // a2 divides b, so cofactor of a2 should be a (rational) number
+       ex ca2, cb2;
+       ex g2 = gcd(a2, b, &ca2, &cb2);
+       if (!is_a<numeric>(ca2)) {
+               cerr << "gcd(" << a2 << ", " << b << ") was miscomputed" << endl;
+               return 1;
+       }
+       ex ca1, cb1;
+       // a1 divides b, so cofactor of a1 should be a (rational) number
+       ex g1 = gcd(a1, b, &ca1, &cb1);
+       if (!is_a<numeric>(ca1)) {
+               cerr << "gcd(" << a1 << ", " << b << ") was miscomputed" << endl;
+               return 1;
+       }
+       return 0;
+}
+