+/*-------------------------------------------------------------------.
+| Return the transpose of R_ARG, of size N. Destroy R_ARG, as it is |
+| replaced with the result. |
+| |
+| R_ARG[I] is NULL or a -1 terminated list of numbers. |
+| |
+| RESULT[NUM] is NULL or the -1 terminated list of the I such as NUM |
+| is in R_ARG[I]. |
+`-------------------------------------------------------------------*/
+
+static short **
+transpose (short **R_arg, int n)
+{
+ /* The result. */
+ short **new_R = XCALLOC (short *, n);
+ /* END_R[I] -- next entry of NEW_R[I]. */
+ short **end_R = XCALLOC (short *, n);
+ /* NEDGES[I] -- total size of NEW_R[I]. */
+ short *nedges = XCALLOC (short, n);
+ int i, j;
+
+ if (trace_flag)