Get lambda reader macro working and fix day 03 bug

[adventofcode2020.git] / src / day03.lisp

diff --git a/src/day03.lisp b/src/day03.lisp
index e708c87565b8bdf730f8f11b4e4276f90493a1b3..093654f6acfe7ba082a2582e3ae957fa3c4e52f5 100644 (file)
--- a/src/day03.lisp
+++ b/src/day03.lisp
@@ -1,23 +1,26 @@
 (asdf:load-system :adventofcode2020)
 (in-package #:adventofcode2020)
+(named-readtables:in-readtable fn-reader)
 
 (defun tree-collisions (slope tree-map)
-  (destructuring-bind (rise run) slope
-    (loop with terrain-width = (-> tree-map first length)
-          for i upfrom 0 by run
-          for j upfrom 0
-          for terrain-line in tree-map
-          when (->> rise (mod j) (= 0))
-          counting (->> terrain-width
-                     (mod i)
-                     (char terrain-line)
-                     (char= #\#)))))
+  (loop with (rise run) = slope
+        with proper-map = (loop for j upfrom 0
+                                for line in tree-map
+                                when (->> rise (mod j) (= 0))
+                                collecting line)
+        with terrain-width = (-> tree-map first length)
+        for i upfrom 0 by run
+        for terrain-line in proper-map
+        counting (->> terrain-width
+                   (mod i)
+                   (char terrain-line)
+                   (char= #\#))))
 
 (day 03 input
   (let ((tree-map (list-from input)))
     (part1 (tree-collisions '(1 3) tree-map))
     (part2 (->> '((1 1) (1 3) (1 5) (1 7) (2 1))
-             (mapcar (fn* (tree-collisions _ tree-map)))
+             (mapcar λ(tree-collisions _ tree-map))
              (reduce #'*)))))
 
 (def-suite day03)
@@ -42,17 +45,17 @@
 (test multiple-collision-check
   (is (equal
         '(2 7 3 4 2)
-        (mapcar (fn* (tree-collisions _ '("..##......."
-                                          "#...#...#.."
-                                          ".#....#..#."
-                                          "..#.#...#.#"
-                                          ".#...##..#."
-                                          "..#.##....."
-                                          ".#.#.#....#"
-                                          ".#........#"
-                                          "#.##...#..."
-                                          "#...##....#"
-                                          ".#..#...#.#")))
+        (mapcar λ(tree-collisions _ '("..##......."
+                                        "#...#...#.."
+                                        ".#....#..#."
+                                        "..#.#...#.#"
+                                        ".#...##..#."
+                                        "..#.##....."
+                                        ".#.#.#....#"
+                                        ".#........#"
+                                        "#.##...#..."
+                                        "#...##....#"
+                                        ".#..#...#.#"))
                 '((1 1) (1 3) (1 5) (1 7) (2 1))))))
 
 (run! 'day03)