demo.scm

@@ -23,20 +23,17 @@
 
 (define (idx->edges i w)
   (filter-map
-   (lambda (offset)
+   (lambda (x y)
-     (let* ([x (idx->x i w)]
+     (if (or (negative? (+ (idx->x i w) x))
-	    [y (idx->y i w)]
+	     (negative? (+ (idx->y i w) y))
-	    [ox (+ x (car offset))]
+	     (>= (+ (idx->x i w) x) w))
-	    [oy (+ y (cdr offset))])
+	 #f
-       (and
+	 (xy->idx
-	(not (negative? ox))
+	  (+ (idx->x i w) x)
-	(not (negative? oy))
+	  (+ (idx->y i w) y)
-	(< ox w)
+	  w)))
-	(xy->idx ox oy w))))
+   '(+0 -1 -1 +1)
-   '(( 0 . -1)
+   '(-1 +0 -1 -1)))
-     (-1 .  0)
-     (-1 . -1)
-     (+1 . -1))))
 
 (define (generate-web w h)
   (define (make-node i)
@@ -45,10 +42,11 @@
 	   (+ (* 30 (idx->y i w)) 10))
      (idx->edges i w)
      white))
+  (reverse
    (let loop ([i 0]
 	      [lst '()])
      (if (>= i (* w h))
-	(reverse lst)
+	 lst
-	(loop (1+ i) (cons (make-node i) lst)))))
+	 (loop (1+ i) (cons (make-node i) lst))))))
 
 (write-graph-to-file (generate-web 5 5) (cadr (command-line)))