Finish day 12

2 files changed, 64 insertions, 2 deletions

diff --git a/aoc-2020-gleam/src/util/dir.gleam b/aoc-2020-gleam/src/util/dir.gleam
new file mode 100644
index 0000000..6f637d9
--- /dev/null
+++ b/aoc-2020-gleam/src/util/dir.gleam
@@ -0,0 +1,41 @@
+import gleam/int
+import gleam/iterator as iter
+import ext/resultx as resx
+import ext/iteratorx as iterx
+import util/pos.{Pos}
+
+pub type Dir {
+  North
+  East
+  South
+  West
+}
+
+pub fn offset(direction: Dir) -> Pos {
+  case direction {
+    North -> #(0, 1)
+    East -> #(1, 0)
+    South -> #(0, -1)
+    West -> #(-1, 0)
+  }
+}
+
+pub fn degree_to_turn(degree: Int) -> Int {
+  resx.assert_unwrap(int.modulo(degree / 90, by: 4))
+}
+
+fn rotate_clockwise_once(direction: Dir) -> Dir {
+  case direction {
+    North -> East
+    East -> South
+    South -> West
+    West -> North
+  }
+}
+
+pub fn rotate_clockwise(this direction: Dir, by times: Int) -> Dir {
+  direction
+  |> iterx.unfold_infinitely(with: rotate_clockwise_once)
+  |> iter.at(times)
+  |> resx.assert_unwrap
+}
diff --git a/aoc-2020-gleam/src/util/pos.gleam b/aoc-2020-gleam/src/util/pos.gleam
index a060440..dd3d01d 100644
--- a/aoc-2020-gleam/src/util/pos.gleam
+++ b/aoc-2020-gleam/src/util/pos.gleam
@@ -1,9 +1,12 @@
+import gleam/int
 import gleam/list
 import gleam/set.{Set}
 
 pub type Pos =
   #(Int, Int)
 
+pub const zero = #(0, 0)
+
 pub const directions8 = [
   #(1, 0),
   #(1, 1),
@@ -19,8 +22,26 @@ pub fn add(p1: Pos, p2: Pos) -> Pos {
   #(p1.0 + p2.0, p1.1 + p2.1)
 }
 
-pub fn neighbours8(pos: Pos) -> Set(Pos) {
+pub fn sub(p1: Pos, p2: Pos) -> Pos {
+  #(p1.0 - p2.0, p1.1 - p2.1)
+}
+
+pub fn mul(p: Pos, by scalar: Int) -> Pos {
+  #(p.0 * scalar, p.1 * scalar)
+}
+
+pub fn neighbours8(p: Pos) -> Set(Pos) {
   directions8
-  |> list.map(with: add(pos, _))
+  |> list.map(with: add(p, _))
   |> set.from_list
 }
+
+pub fn manhattan_dist(from p1: Pos, to p2: Pos) -> Int {
+  int.absolute_value(p1.0 - p2.0) + int.absolute_value(p1.1 - p2.1)
+}
+
+pub fn rotate_around_origin(this p: Pos, by times: Int) -> Pos {
+  let assert Ok(sin) = list.at([0, -1, 0, 1], times)
+  let assert Ok(cos) = list.at([1, 0, -1, 0], times)
+  #(p.0 * cos - p.1 * sin, p.0 * sin + p.1 * cos)
+}