firstie

quad/quadwriter/query.rkt

@@ -40,8 +40,9 @@
   (define qi (match quad-or-index
                [(? quad? q) (make-query-index q)]
                [idx idx]))
-  (for/fold ([qs (query-index-forward qi)]
+  (define vec (list->vector (query-index-forward qi)))
-             #:result (and qs (car qs)))
+  (for/fold ([vidx 0]
+             #:result (and vidx (vector-ref vec vidx)))
             ([query-piece (in-list (parse-query query-str))])
     (match query-piece
       [(cons pred 'this)
@@ -50,13 +51,17 @@
        ;; once we have this-thing, locate it in the forward index and keep going
        (memq this-thing (query-index-forward qi))]
       [(cons pred count)
-       (let loop ([qs qs][seen 0])
+       (let loop ([vidx vidx][seen 0])
-         (define maybe-tail (memf pred qs))
+         (define idx (for*/first ([vi (in-range vidx (vector-length vec))]
-         (and maybe-tail
+                                  [val (in-value (vector-ref vec vi))]
+                                  #:when (pred val))
+                       vi))
+                                        
+         (and idx
               (let ([seen (add1 seen)])
                 (cond
-                  [(= seen count) maybe-tail]
+                  [(= seen count) idx]
-                  [else (loop (cdr maybe-tail) seen)]))))])))
+                  [else (loop (add1 idx) seen)]))))])))
           
 (module+ test
   (require rackunit)