1 files changed, 59 insertions, 0 deletions
diff --git a/2021/13/code.tl b/2021/13/code.tl
new file mode 100644
index 0000000..f222e27
--- /dev/null
+++ b/2021/13/code.tl
@@ -0,0 +1,59 @@
+(defstruct board ()
+  (w 0)
+  (h 0)
+  (a (hash))
+
+  (:method print (bo stream pretty-p)
+    (put-line `board @{bo.w}x@{bo.h}:`)
+    (each ((y 0..bo.h))
+      (each ((x 0..bo.w))
+        (put-char (if [bo x y] #\# #\space) stream))
+      (put-line)))
+
+  (:method lambda (bo x y)
+    [(or [bo.a y] nil) x])
+
+  (:method lambda-set (bo x y nv)
+    (let ((row (or [bo.a y]
+                   (set [bo.a y] (hash)))))
+      (set [row x] nv)
+      (upd bo.h (max (succ y)))
+      (upd bo.w (max (succ x)))))
+
+  (:method fold-y (bo yline)
+    (let ((a bo.a))
+      (del [a yline])
+      (set bo.h yline)
+      (dohash (y row a bo)
+        (when (> y yline)
+          (let ((ry (- (* 2 yline) y)))
+            (if [a ry]
+              (set [a ry]
+                   [hash-uni [a ry] [a y] or])
+              (set [a ry] row)))
+          (del [a y])))))
+
+  (:method fold-x (bo xline)
+    (let ((a bo.a))
+      (dohash (y row a bo)
+        (each ((x (succ xline)..bo.w))
+          (when [row x]
+            (set [row (- (* 2 xline) x)] t)
+            (del [row x])))))
+    (set bo.w xline))
+
+  (:method count (bo)
+    (let ((count 0))
+      (dohash (y row bo.a count)
+        (dohash (x v row)
+          (if v (inc count)))))))
+
+(defun solve-two (: (name "input"))
+  (let ((bo (new board)))
+    (each ((line (file-get-lines name)))
+      (match-case line
+        (`@x,@y` (set [bo (toint x) (toint y)] t))
+        (`fold along x=@x` bo.(fold-x (toint x)))
+        (`fold along y=@y` bo.(fold-y (toint y)))))
+    (print bo)
+    nil))