From 880cfd5c71f4bec606520d3803d9242fb570e6d9 Mon Sep 17 00:00:00 2001
From: Matthew Butterick <mb@mbtype.com>
Date: Mon, 9 Dec 2019 07:19:59 -0800
Subject: [PATCH] d09 pt2

---
 2019/09.rkt | 67 ++++++++++++++++++++++++++---------------------------
 1 file changed, 33 insertions(+), 34 deletions(-)

diff --git a/2019/09.rkt b/2019/09.rkt
index 3766707..eaeb13a 100644
--- a/2019/09.rkt
+++ b/2019/09.rkt
@@ -9,22 +9,14 @@
 (define (make-runner program [calling-thd (current-thread)])
   (thread (λ ()
             (define regs (string->regs program))
-            (define (grow-regs! len)
-              (define newvec (make-vector (add1 len) 0))
-              (vector-copy! newvec 0 regs)
-              (set! regs newvec))
-            (define (reg-ref ptr)
-              (cond
-                [(< ptr (vector-length regs)) (vector-ref regs ptr)]
-                [else
-                 (grow-regs! (add1 ptr))
-                 (reg-ref ptr)]))
-            (define (reg-set! ptr val)
-              (cond
-                [(< ptr (vector-length regs)) (vector-set! regs ptr val)]
-                [else
-                 (grow-regs! (add1 ptr))
-                 (reg-set! ptr val)]))
+            (define (maybe-enlarge-regs len)
+              (unless (< len (vector-length regs))
+                (define newvec (make-vector (add1 len) 0))
+                (vector-copy! newvec 0 regs)
+                (set! regs newvec))
+              regs)
+            (define (reg-ref ptr) (vector-ref (maybe-enlarge-regs ptr) ptr))
+            (define (reg-set! ptr val) (vector-set! (maybe-enlarge-regs ptr) ptr val))
             (define relative-base 0)
             (let/ec terminate
               (let loop ([ptr 0])
@@ -36,36 +28,35 @@
                      (cons (+ (* 10 d1) d0)
                            (for/list ([mode-val (list d2 d3 d4)]
                                       [offset '(1 2 3)])
-                             (λ (ptr [io-mode? 'read])
-                               ((if (eq? io-mode? 'read) reg-ref values)
-                                (let ([ptr-adjusted (+ ptr offset)])
-                                  (match mode-val
-                                    [0 (reg-ref ptr-adjusted)] ; position
-                                    [1 ptr-adjusted] ; immediate
-                                    [2 (+ relative-base (reg-ref ptr-adjusted))]))))))])) ; relative
+                             (λ (ptr)
+                               (define ptr-adjusted (+ ptr offset))
+                               (match mode-val
+                                 [0 (reg-ref ptr-adjusted)] ; position
+                                 [1 ptr-adjusted] ; immediate
+                                 [2 (+ relative-base (reg-ref ptr-adjusted))]))))])) ; relative
                 (define next-ptr
                   (match opcode
                     [(or 1 2 7 8) ; 4-arity: add & multiply & compare
-                     (reg-set! (mode-3 ptr 'write) ((match opcode
-                                                  [1 +]
-                                                  [2 *]
-                                                  [7 (binarize <)]
-                                                  [8 (binarize =)]) (mode-1 ptr) (mode-2 ptr)))
+                     (reg-set! (mode-3 ptr) ((match opcode
+                                               [1 +]
+                                               [2 *]
+                                               [7 (binarize <)]
+                                               [8 (binarize =)]) (reg-ref (mode-1 ptr)) (reg-ref (mode-2 ptr))))
                      (+ ptr 4)]
                     [(or 3 4 9) ; 2-arity: input & output
                      (match opcode
-                       [3 (reg-set! (mode-1 ptr 'write) (thread-receive))]
-                       [4 (thread-send calling-thd (mode-1 ptr))]
-                       [9 (set! relative-base (+ relative-base (mode-1 ptr)))])
+                       [3 (reg-set! (mode-1 ptr) (thread-receive))]
+                       [4 (thread-send calling-thd (reg-ref (mode-1 ptr)))]
+                       [9 (set! relative-base (+ relative-base (reg-ref (mode-1 ptr))))])
                      (+ ptr 2)]
                     [(or 5 6) ; 3-arity: jump
                      (if ((match opcode
                             [5 not]
-                            [6 values]) (zero? (mode-1 ptr)))
-                         (mode-2 ptr)
+                            [6 values]) (zero? (reg-ref (mode-1 ptr))))
+                         (reg-ref (mode-2 ptr))
                          (+ ptr 3))]
                     [99 (thread-send calling-thd 'done) (terminate)]
-                    [_ (error "unknown-opcode" opcode)]))
+                    [_ (error "unknown opcode" opcode)]))
                 (loop next-ptr))))))
 
 
@@ -92,8 +83,16 @@
  (run "104,1125899906842624,99")
  '(1125899906842624))
 
+;; 1
 (define t1 (make-runner (file->string "09.rktd")))
 (thread-send t1 1)
 (check-equal?
  (run t1)
  '(3601950151))
+
+;; 2
+(define t2 (make-runner (file->string "09.rktd")))
+(thread-send t2 2)
+(check-equal?
+ (run t2)
+ '(64236))
\ No newline at end of file