From 2a4ca8b9dfcc229ea4f4e786990cdb1079b17d03 Mon Sep 17 00:00:00 2001
From: Matthew Butterick <mb@mbtype.com>
Date: Fri, 14 Feb 2020 21:04:13 -0800
Subject: [PATCH] firstie

---
 quad/quadwriter/query.rkt | 41 ++++++++++++++++++++++-----------------
 1 file changed, 23 insertions(+), 18 deletions(-)

diff --git a/quad/quadwriter/query.rkt b/quad/quadwriter/query.rkt
index 0e118fcc..60865696 100644
--- a/quad/quadwriter/query.rkt
+++ b/quad/quadwriter/query.rkt
@@ -10,7 +10,7 @@
   (define qs (let loop ([q q])
                (cons q (append* (for/list ([elem (in-list (quad-elems q))]
                                            #:when (quad? elem))
-                                          (loop elem))))))
+                                  (loop elem))))))
   (query-index qs (reverse qs)))
 
 (define (string->key str #:this [this? #false])
@@ -31,17 +31,18 @@
 
 (define (parse-query str)
   (for/list ([piece (in-list (string-split str ":"))])
-            (match (regexp-match #px"^(.*)\\[(.*?)\\]$" piece)
-              [#false (cons (string->key piece) #false)]
-              [(list _ name arg) (cons (hash-ref preds (string->key name)) (or (string->number arg)
-                                                                               (string->symbol arg)))])))
+    (match (regexp-match #px"^(.*)\\[(.*?)\\]$" piece)
+      [#false (cons (string->key piece) #false)]
+      [(list _ name arg) (cons (hash-ref preds (string->key name)) (or (string->number arg)
+                                                                       (string->symbol arg)))])))
 
 (define (query quad-or-index query-str [querying-q #false])
   (define qi (match quad-or-index
                [(? quad? q) (make-query-index q)]
                [idx idx]))
-  (for/fold ([qs (query-index-forward qi)]
-             #:result (and qs (car qs)))
+  (define vec (list->vector (query-index-forward qi)))
+  (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])
-         (define maybe-tail (memf pred qs))
-         (and maybe-tail
+       (let loop ([vidx vidx][seen 0])
+         (define idx (for*/first ([vi (in-range vidx (vector-length vec))]
+                                  [val (in-value (vector-ref vec vi))]
+                                  #:when (pred val))
+                       vi))
+                                        
+         (and idx
               (let ([seen (add1 seen)])
                 (cond
-                  [(= seen count) maybe-tail]
-                  [else (loop (cdr maybe-tail) seen)]))))])))
+                  [(= seen count) idx]
+                  [else (loop (add1 idx) seen)]))))])))
           
 (module+ test
   (require rackunit)
@@ -65,12 +70,12 @@
   (define-syntax-rule (factory type proc)
     (make-quad #:type type
                #:elems (for/list ([i (in-range 3)])
-                                 (set! counter (add1 counter))
-                                 (define new-q (proc))
-                                 (quad-update! new-q
-                                               [tag (format "~a[~a]-~a" 'proc counter (gensym))])
-                                 (hash-set! (quad-attrs new-q) 'count counter)
-                                 new-q)))
+                         (set! counter (add1 counter))
+                         (define new-q (proc))
+                         (quad-update! new-q
+                                       [tag (format "~a[~a]-~a" 'proc counter (gensym))])
+                         (hash-set! (quad-attrs new-q) 'count counter)
+                         new-q)))
 
   (define (line) (make-quad #:type line-quad))
   (define (block) (factory block-quad line))