Remove a section of the web

graphgif.scm

@@ -113,6 +113,28 @@
 	(reverse lst)
 	(loop (1+ i) (cons (make-node i) lst)))))
 
+(define-public (remove-rect graph w x1 y1 x2 y2)
+  ;; Assumption is that is a graph generated by generate-web
+  ;; and that it has not been re-indexed
+  ;; x1 < x2, y1 < y2
+  (define edges-to-remove
+    (unfold (lambda (s) (> s (xy->idx x2 y2 w)))
+	    identity
+	    (lambda (s) (if (>= (idx->x s w) x2)
+			    (xy->idx x1 (1+ (idx->y s w)) w)
+			    (1+ s)))
+	    (xy->idx x1 y1 w)))
+  (filter-map
+   (lambda (idx/node)
+     (if (memq (car idx/node) edges-to-remove)
+	 #f
+	 (cons (car idx/node)
+	       (set-node-edges (cdr idx/node)
+			       (remove
+				(lambda (edge) (memq edge edges-to-remove))
+				(node-edges (cdr idx/node)))))))
+   graph))
+
 ;;;;;;;;;;;;
 ;; Output ;;
 ;;;;;;;;;;;;