X-Git-Url: https://www.ginac.de/ginac.git//ginac.git?p=ginac.git;a=blobdiff_plain;f=ginac%2Fnormal.cpp;h=a8a1e1eb1bd3f7282418eff3160f2ba1a25114e6;hp=439a644606388ad1f70fc08d1d537f3a7189a7be;hb=ec3f0adc471cd6205e81115111070421c8477c6e;hpb=227c0507d513360c31cd16484e08215e1a506363

diff --git a/ginac/normal.cpp b/ginac/normal.cpp
index 439a6446..a8a1e1eb 100644
--- a/ginac/normal.cpp
+++ b/ginac/normal.cpp
@@ -1771,7 +1771,7 @@ ex lcm(const ex &a, const ex &b, bool check_args)
  *  Yun's algorithm.  Used internally by sqrfree().
  *
  *  @param a  multivariate polynomial over Z[X], treated here as univariate
- *            polynomial in x.
+ *            polynomial in x (needs not be expanded).
  *  @param x  variable to factor in
  *  @return   vector of factors sorted in ascending degree */
 static exvector sqrfree_yun(const ex &a, const symbol &x)
@@ -1780,6 +1780,9 @@ static exvector sqrfree_yun(const ex &a, const symbol &x)
 	ex w = a;
 	ex z = w.diff(x);
 	ex g = gcd(w, z);
+	if (g.is_zero()) {
+		return res;
+	}
 	if (g.is_equal(_ex1)) {
 		res.push_back(a);
 		return res;
@@ -1787,6 +1790,9 @@ static exvector sqrfree_yun(const ex &a, const symbol &x)
 	ex y;
 	do {
 		w = quo(w, g, x);
+		if (w.is_zero()) {
+			return res;
+		}
 		y = quo(z, g, x);
 		z = y - w.diff(x);
 		g = gcd(w, z);
@@ -1798,7 +1804,7 @@ static exvector sqrfree_yun(const ex &a, const symbol &x)
 
 /** Compute a square-free factorization of a multivariate polynomial in Q[X].
  *
- *  @param a  multivariate polynomial over Q[X]
+ *  @param a  multivariate polynomial over Q[X] (needs not be expanded)
  *  @param l  lst of variables to factor in, may be left empty for autodetection
  *  @return   a square-free factorization of \p a.
  *
@@ -1833,8 +1839,8 @@ static exvector sqrfree_yun(const ex &a, const symbol &x)
  */
 ex sqrfree(const ex &a, const lst &l)
 {
-	if (is_exactly_a<numeric>(a) ||     // algorithm does not trap a==0
-	    is_a<symbol>(a))        // shortcut
+	if (is_exactly_a<numeric>(a) ||
+	    is_a<symbol>(a))        // shortcuts
 		return a;
 
 	// If no lst of variables to factorize in was specified we have to