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Stop failing assertions when we encounter an insoluble puzzle.

[originally from svn r7408]

--- a/rect.c

+++ b/rect.c

@@ -329,6 +329,11 @@

     number->npoints--;

 }

+/*

+ * Returns 0 for failure to solve due to inconsistency; 1 for

+ * success; 2 for failure to complete a solution due to either

+ * ambiguity or it being too difficult.

+ */

 static int rect_solver(int w, int h, int nrects, struct numberdata *numbers,

                        unsigned char *hedge, unsigned char *vedge,

 		       random_state *rs)

@@ -434,6 +439,14 @@

      * Indexing of this array is by the formula

      * 

      *   overlaps[(rectindex * h + y) * w + x]

+     * 

+     * A positive or zero value indicates what it sounds as if it

+     * should; -1 indicates that this square _cannot_ be part of

+     * this rectangle; and -2 indicates that it _definitely_ is

+     * (which is distinct from 1, because one might very well know

+     * that _if_ square S is part of rectangle R then it must be

+     * because R is placed in a certain position without knowing

+     * that it definitely _is_).

      */

     overlaps = snewn(nrects * w * h, int);

     memset(overlaps, 0, nrects * w * h * sizeof(int));

@@ -526,7 +539,10 @@

                 if (overlaps[(i * h + y) * w + x] >= -1) {

                     int j;

-                    assert(overlaps[(i * h + y) * w + x] > 0);

+                    if (overlaps[(i * h + y) * w + x] <= 0) {

+                        ret = 0;       /* inconsistency */

+                        goto cleanup;

+                    }

 #ifdef SOLVER_DIAGNOSTICS

                     printf("marking %d,%d as known for rect %d"

                            " (sole remaining number position)\n", x, y, i);

@@ -568,7 +584,10 @@

             for (yy = miny; yy < maxy; yy++)

                 for (xx = minx; xx < maxx; xx++)

                     if (overlaps[(i * h + yy) * w + xx] >= -1) {

-                        assert(overlaps[(i * h + yy) * w + xx] > 0);

+                        if (overlaps[(i * h + yy) * w + xx] <= 0) {

+                            ret = 0;   /* inconsistency */

+                            goto cleanup;

+                        }

 #ifdef SOLVER_DIAGNOSTICS

                         printf("marking %d,%d as known for rect %d"

                                " (intersection of all placements)\n",

@@ -847,15 +866,17 @@

         }

     }

-    ret = TRUE;

+    cleanup:

+    ret = 1;

     for (i = 0; i < nrects; i++) {

 #ifdef SOLVER_DIAGNOSTICS

         printf("rect %d has %d possible placements\n",

                i, rectpositions[i].n);

 #endif

-        assert(rectpositions[i].n > 0);

-        if (rectpositions[i].n > 1) {

-            ret = FALSE;

+        if (rectpositions[i].n <= 0) {

+            ret = 0;                   /* inconsistency */

+        } else if (rectpositions[i].n > 1) {

+            ret = 2;                   /* remaining uncertainty */

         } else if (hedge && vedge) {

             /*

              * Place the rectangle in its only possible position.

@@ -1639,9 +1660,9 @@

 		ret = rect_solver(params->w, params->h, nnumbers, nd,

 				  NULL, NULL, rs);

 	    else

-		ret = TRUE;	       /* allow any number placement at all */

+		ret = 1;	       /* allow any number placement at all */

-            if (ret) {

+            if (ret == 1) {

                 /*

                  * Now place the numbers according to the solver's

                  * recommendations.