From 9bc43809efeb983f8aad0f1062282164982b3ba9 Mon Sep 17 00:00:00 2001
From: Matthew Butterick <mb@mbtype.com>
Date: Fri, 16 Dec 2016 22:31:25 -0800
Subject: [PATCH] start day16

---
 2016/day16/input-b.rkt |  2 ++
 2016/day16/input.rkt   |  2 ++
 2016/day16/lang.rkt    | 38 ++++++++++++++++++++++++++++++++++++++
 2016/day16/test-b.rkt  |  2 ++
 2016/day16/test.rkt    |  2 ++
 5 files changed, 46 insertions(+)
 create mode 100644 2016/day16/input-b.rkt
 create mode 100644 2016/day16/input.rkt
 create mode 100644 2016/day16/lang.rkt
 create mode 100644 2016/day16/test-b.rkt
 create mode 100644 2016/day16/test.rkt

diff --git a/2016/day16/input-b.rkt b/2016/day16/input-b.rkt
new file mode 100644
index 0000000..c37fcbe
--- /dev/null
+++ b/2016/day16/input-b.rkt
@@ -0,0 +1,2 @@
+#lang reader "lang.rkt"
+35651584, 10010000000110000
\ No newline at end of file
diff --git a/2016/day16/input.rkt b/2016/day16/input.rkt
new file mode 100644
index 0000000..fbd18e6
--- /dev/null
+++ b/2016/day16/input.rkt
@@ -0,0 +1,2 @@
+#lang reader "lang.rkt"
+272, 10010000000110000
\ No newline at end of file
diff --git a/2016/day16/lang.rkt b/2016/day16/lang.rkt
new file mode 100644
index 0000000..d7ea2e6
--- /dev/null
+++ b/2016/day16/lang.rkt
@@ -0,0 +1,38 @@
+#lang br/quicklang ;; http://adventofcode.com/2016/day/16
+(require openssl/md5)
+(provide read-syntax
+         (rename-out [mb #%module-begin]))
+
+(define (read-syntax path port)
+  (strip-bindings
+   #`(module mod "lang.rkt"
+       #,@(string-split (string-trim (port->string port)) ", "))))
+
+(define-macro (mb SIZE INIT)
+  #'(#%module-begin
+     (display (list->string (checksum (fill-disk (string->list INIT) (string->number SIZE)))))))
+
+(define (dragonize cs)
+  (append cs '(#\0)
+          (for/list ([c (in-list (reverse cs))])
+            (if (eqv? c #\1)
+                #\0
+                #\1))))
+
+(define (fill-disk init size)
+  (let loop ([cs init])
+    (if (>= (length cs) size)
+        (take cs size)
+        (loop (dragonize cs)))))
+
+(require sugar/list)
+(define (checksum cs)
+  (let loop ([cs cs])
+    (if (odd? (length cs))
+        cs
+        (loop
+         (for/list ([match (in-list (slice-at cs 2))])
+           (if (member match '((#\0 #\0) (#\1 #\1)))
+               #\1
+               #\0))))))
+  
diff --git a/2016/day16/test-b.rkt b/2016/day16/test-b.rkt
new file mode 100644
index 0000000..238af15
--- /dev/null
+++ b/2016/day16/test-b.rkt
@@ -0,0 +1,2 @@
+#lang reader "lang.rkt"
+20, 10000
\ No newline at end of file
diff --git a/2016/day16/test.rkt b/2016/day16/test.rkt
new file mode 100644
index 0000000..93b5eb8
--- /dev/null
+++ b/2016/day16/test.rkt
@@ -0,0 +1,2 @@
+#lang reader "lang.rkt"
+12, 110010110100
\ No newline at end of file