X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?p=moebius2.git;a=blobdiff_plain;f=mgraph.h;h=85f1a3c8d0ef621e8417a2715c1af014df187e91;hp=de26852f9974aef3960c09e4e2acff63ffb17537;hb=f5c44e57feae26a81c416d9d7cc69f0accbac8b6;hpb=62f97dcbc53754ef8a81add86946e54825c4c096

diff --git a/mgraph.h b/mgraph.h
index de26852..85f1a3c 100644
--- a/mgraph.h
+++ b/mgraph.h
@@ -4,62 +4,64 @@
 /*
  * Vertices in strip are numbered as follows:
  *
- *			  |
+ *                          :axis of symmetry
+ *			  | :
+ *			  | :
  *     ___ X-2 ___ X-1 ___| 0  ___  1  ___  2  ___  3  ___  4  __
- *         Y-1     Y-1    |0       0       0       0       0
- *        /  \    /  \    /  \    /  \    /  \    /  \    /  \
- *       /    \  /    \  /|   \  /    \  /    \  /    \  /    \
+ *         Y-1     Y-1    |0:      0       0       0       0
+ *        /  \    /  \    / :\    /  \    /  \    /  \    /  \
+ *       /    \  /    \  /| : \  /    \  /    \  /    \  /    \
  *     X-3 ___ X-2 ___ X-1|___  0  ___  1  ___  2  ___  3  ___  4
- *     Y-2     Y-2     Y-2|    1       1       1       1       1
- *       \    /  \    /  \|   /  \    /  \    /  \    /  \    /
- *        \  /    \  /    \  /    \  /    \  /    \  /    \  /
+ *     Y-2     Y-2     Y-2| :  1       1       1       1       1
+ *       \    /  \    /  \| : /  \    /  \    /  \    /  \    /
+ *        \  /    \  /    \ :/    \  /    \  /    \  /    \  /
  *     ___ X-2 ___ X-1 ___| 0  ___  1  ___  2  ___  3  __   4 ___
- *         Y-3     Y-3    |2       2       2       2 	   2
- *        /  \    /  \    /  \    /  \    /  \    /  \    /  \
- *       /    \  /    \  /|   \  /    \  /    \  /    \  /    \
+ *         Y-3     Y-3    |2:      2       2       2 	   2
+ *        /  \    /  \    / :\    /  \    /  \    /  \    /  \
+ *       /    \  /    \  /| : \  /    \  /    \  /    \  /    \
  *     X-3 ___ X-2 ___ X-1|___  0  ___  1  ___  2  ___  3  ___  4
- *     Y-4     Y-4     Y-4|    3       3       3       3       3
- *			  |
- *       .   .   .   .   .|  .   .   .   .   .   .   .   .   .   .
- *			  |
+ *     Y-4     Y-4     Y-4| :  3       3       3       3       3
+ *			  | :
+ *       .   .   .   .   .| :.   .   .   .   .   .   .   .   .   .
+ *			  | :
  *     ___ X-2 ___ X-1 ___| 0  ___  1  ___  2  ___  3  ___  4 ___
  *         2       2      |Y-3     Y-3     Y-3     Y-3     Y-3
- *        /  \    /  \    /  \    /  \    /  \    /  \    /  \
- *       /    \  /    \  /|   \  /    \  /    \  /    \  /    \
+ *        /  \    /  \    / :\    /  \    /  \    /  \    /  \
+ *       /    \  /    \  /| : \  /    \  /    \  /    \  /    \
  *          __ X-2 ___ X-1|___  0  ___  1  ___  2  ___  3  ___  3  ___  4
- *             1       1  |    Y-2     Y-2     Y-2     Y-2     Y-2     Y-2
- *    /  \    /  \    /  \|   /  \    /  \    /	 \    /  \    /
- *   /    \  /    \  /    \  /    \  /    \  /	  \  /    \  /
+ *             1       1  | :  Y-2     Y-2     Y-2     Y-2     Y-2     Y-2
+ *    /  \    /  \    /  \| : /  \    /  \    /	 \    /  \    /
+ *   /    \  /    \  /    \ :/    \  /    \  /	  \  /    \  /
  *  -3 ___ X-2 ___ X-1 ___| 0  ___  1  ___  2  ___  3  ___  4 ___
  *  0      0       0      |Y-1     Y-1     Y-1     Y-1     Y-1
+ *			  | :
+ *			  | :
  *			  |
+ *                        ^ join, where there is
+ *                           a discontinuity in numbering
+ *
  * Node x,y for
- *   0 <= x < X     x = distance along
- *   0 <= y < Y     y = distance across
+ *   0 <= x < X = 2^XBITS     x = distance along
+ *   0 <= y < Y = 2^YBITS-1   y = distance across
  *
  * Vertices are in reading order from diagram above ie x varies fastest.
  *
- * Y must be even.  The actual location opposite (0,0) is (X-(Y-1)/2,0),
- * and likewise opposite (0,Y-1) is ((Y-1)/2,0).
- *
  * Note that though presentation above is equilateral triangles, this
  * is not the case.  It's actually a square lattice with half of the
  * diagonals added.  We can't straighten it out because at the join
  * the diagonals point the other way!
  *
- * We label edges as follows:        Or in the square view:
+ * We label edges as follows:
  *
- *		    \2   /1                 2  1
- *		     \  /	            | /
- *		  ___ 0   __	            |/
- *		  3    1   0	         3--*--0
- *		     /  \	           /|
- *		   4/   5\	          / |
- *				         4  5
+ *		    \2   /1
+ *		     \  /
+ *		  ___ 0   __
+ *		  3    1   0
+ *		     /  \
+ *		   4/   5\
  *
- *                                   (This makes the numbering
- *                                   discontinuity, at the join,
- *                                   vertical and thus tractable.)
+ * vertex number:   0000 | y      | x
+ *                        (YBITS)   XBITS
  */
 
 #ifndef MGRAPH_H
@@ -67,26 +69,25 @@
 
 #include "common.h"
 
-#define DIMBITS 4
-
-#define XBITS DIMBITS
-#define X (1<<XBITS)
-#define YBITS DIMBITS
+#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  (DEFSZ % 10)
+#define Y      ((DEFSZ / 10)*2+1)
+#endif
 
-/* vertex number:   0000 | y     | x
- *                        YBITS   XBITS
- */
+#define X (1<<XBITS)
 
 #define N (X*Y)
 #define XMASK (X-1)
 #define YSHIFT XBITS
 #define Y1 (1 << YSHIFT)
-#define YMASK (Y << YSHIFT)
-
-#define DIM (N*D3)
 
 #define V6 6
+#define V3 3
 
 #define FOR_VERTEX(v) \
   for ((v)=0; (v)<N; (v)++)
@@ -94,10 +95,16 @@
 #define FOR_VPEDGE(v,e) \
   for ((e)=0; (e)<V6; (e)++)
 
-extern int edge_end2(unsigned v1, int e);
+int edge_end2(unsigned v1, int e);
 #define EDGE_END2 edge_end2
 
-#define RIM_VERTEX_P(v) (((v) & YMASK) == 0 || ((v) & YMASK) == (Y-1)*Y1)
+/* 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 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))				\
@@ -119,5 +126,6 @@ extern int edge_end2(unsigned v1, int e);
     for ((vx)=0; (v)= (vy)<<YSHIFT | (vx), (vx)<X; (vx)++)
 
 typedef double Vertices[N][D3];
+struct Vertices { Vertices a; };
 
 #endif /*MGRAPH_H*/