X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?p=moebius2.git;a=blobdiff_plain;f=mgraph.h;h=85f1a3c8d0ef621e8417a2715c1af014df187e91;hp=e98fa850a53658bacf17ff452d03d2341c89afa9;hb=f5c44e57feae26a81c416d9d7cc69f0accbac8b6;hpb=3a831ca9695bf1befddb9d73c5cc8cdb34b6e92e

diff --git a/mgraph.h b/mgraph.h
index e98fa85..85f1a3c 100644
--- a/mgraph.h
+++ b/mgraph.h
@@ -60,8 +60,8 @@
  *		     /  \
  *		   4/   5\
  *
- * vertex number:   0000 | y     | x
- *                        YBITS   XBITS
+ * vertex number:   0000 | y      | x
+ *                        (YBITS)   XBITS
  */
 
 #ifndef MGRAPH_H
@@ -69,24 +69,25 @@
 
 #include "common.h"
 
-#ifndef DEFBITS
+#ifndef DEFSZ /* DEFSZ may be (Y/2-1)*10 + XBITS ie Y is 2*<tens>+1 */
 #define XBITS 3
 #define YBITS 3
+#define Y ((1<<YBITS) - 1)
+#define YMASK (Y << YSHIFT)
 #else
-#define XBITS (DEFBITS / 10)
-#define YBITS (DEFBITS % 10)
+#define XBITS  (DEFSZ % 10)
+#define Y      ((DEFSZ / 10)*2+1)
 #endif
 
 #define X (1<<XBITS)
-#define Y ((1<<YBITS) - 1)
 
 #define N (X*Y)
 #define XMASK (X-1)
 #define YSHIFT XBITS
 #define Y1 (1 << YSHIFT)
-#define YMASK (Y << YSHIFT)
 
 #define V6 6
+#define V3 3
 
 #define FOR_VERTEX(v) \
   for ((v)=0; (v)<N; (v)++)
@@ -97,11 +98,13 @@
 int edge_end2(unsigned v1, int e);
 #define EDGE_END2 edge_end2
 
-/* given v1,e  s.t.  v2==EDGE_END2(v1,e) >= 0,
- * returns  eprime s.t. v1==EDGE_END2(v2,eprime) */
+/* given    v1,e     s.t.  v2==EDGE_END2(v1,e) >= 0,
+ * returns  eprime   s.t.  v1==EDGE_END2(v2,eprime) */
 int edge_reverse(int v1, int e);
 
-#define RIM_VERTEX_P(v) (((v) & YMASK) == 0 || ((v) & YMASK) == (Y-1)*Y1)
+#define EDGE_OPPOSITE(e) (((e)+V3) % V6)
+
+#define RIM_VERTEX_P(v) (((v) & ~XMASK) == 0 || ((v) & ~XMASK) == (Y-1)*Y1)
 
 #define FOR_VEDGE_X(v1,e,v2,init,otherwise)	\
   FOR_VPEDGE((v1),(e))				\