1 files changed, 27 insertions, 0 deletions
diff --git a/aoc-2020-gleam/src/util/hex.gleam b/aoc-2020-gleam/src/util/hex.gleam
index 21db192..070b6e4 100644
--- a/aoc-2020-gleam/src/util/hex.gleam
+++ b/aoc-2020-gleam/src/util/hex.gleam
@@ -1,3 +1,8 @@
+import gleam/bool
+import gleam/list
+import gleam/set.{type Set}
+import ext/setx
+
 pub opaque type Hex {
   Hex(q: Int, r: Int, s: Int)
 }
@@ -19,3 +24,25 @@ pub const ne = Hex(q: 1, r: -1, s: 0)
 pub fn add(a: Hex, b: Hex) -> Hex {
   Hex(q: a.q + b.q, r: a.r + b.r, s: a.s + b.s)
 }
+
+fn directions7() -> Set(Hex) {
+  set.from_list({
+    use q <- list.flat_map([-1, 0, 1])
+    use r <- list.flat_map([-1, 0, 1])
+    use s <- list.flat_map([-1, 0, 1])
+    use <- bool.guard(when: q + r + s != 0, return: [])
+    [Hex(q, r, s)]
+  })
+}
+
+fn directions6() -> Set(Hex) {
+  set.delete(from: directions7(), this: zero)
+}
+
+pub fn neighbours6(h: Hex) -> Set(Hex) {
+  setx.map(directions6(), with: add(h, _))
+}
+
+pub fn neighbours7(h: Hex) -> Set(Hex) {
+  setx.map(directions7(), with: add(h, _))
+}