Finish day 9

1 files changed, 13 insertions, 0 deletions

diff --git a/aoc-2020-gleam/src/ext/iteratorx.gleam b/aoc-2020-gleam/src/ext/iteratorx.gleam
index 0ef5d51..65e06f2 100644
--- a/aoc-2020-gleam/src/ext/iteratorx.gleam
+++ b/aoc-2020-gleam/src/ext/iteratorx.gleam
@@ -10,3 +10,16 @@ pub fn count(iterator: Iterator(a), satisfying predicate: fn(a) -> Bool) -> Int
   |> iter.filter(for: predicate)
   |> length
 }
+
+pub fn filter_map(
+  iterator: Iterator(a),
+  with mapper: fn(a) -> Result(b, c),
+) -> Iterator(b) {
+  iterator
+  |> iter.flat_map(with: fn(elem) {
+    case mapper(elem) {
+      Ok(new) -> iter.single(new)
+      Error(_) -> iter.empty()
+    }
+  })
+}