cameo: added optimization of movements between tool paths

- ops.h, ops.c (optimize_paths): reorder toolpaths to reduce the distance
  between them
- lang.l, lang.y: added command "optimize"
- README: documented "optimize"

cameo/ops.c

@@ -12,6 +12,7 @@
 
 
 #include <stddef.h>
+#include <math.h>
 
 #include "path.h"
 #include "shape.h"
@@ -88,3 +89,48 @@ struct path *try_mill(struct path *path, double diam, double step)
 		    path->first->z, path->r_tool, diam/2, step);
 	return NULL;
 }
+
+
+/*
+ * This isn't a perfect solution for the traveling salesman problem, but it's
+ * easy to implement and usually produces results that don't look overly
+ * offensive.
+ */
+
+struct path *optimize_paths(struct path *paths)
+{
+	struct path **walk, **best = NULL;
+	struct path *res = NULL, **anchor = &res;
+	struct path *curr;
+	struct point *p;
+	double best_d = 0, d;
+
+	for (walk = &paths; *walk; walk = &(*walk)->next) {
+		p = (*walk)->first;
+		if (!p)
+			continue;
+		d = hypot(p->x, p->y);
+		if (!best || d  < best_d) {
+			best = walk;
+			best_d = d;
+		}
+	}
+	while (best) {
+		curr = *best;
+		*anchor = *best;
+		anchor = &curr->next;
+		*best = curr->next;
+		best = NULL;
+		for (walk = &paths; *walk; walk = &(*walk)->next) {
+			p = (*walk)->first;
+			if (!p)
+				continue;
+			d = hypot(p->x-curr->last->x, p->y-curr->last->y);
+			if (!best || d < best_d) {
+				best = walk;
+				best_d = d;
+			}
+		}
+	}
+	return res;
+}