resistor-color

resistor-color/src/resistor_color.gleam

@@ -0,0 +1,42 @@
+pub type Color {
+  Black
+  Brown
+  Red
+  Orange
+  Yellow
+  Green
+  Blue
+  Violet
+  Grey
+  White
+}
+
+pub fn code(color: Color) -> Int {
+  case find_index(colors(), fn(c) { c == color }) {
+    Error(_) -> -1
+    Ok(code) -> code
+  }
+}
+
+pub fn colors() -> List(Color) {
+  [Black, Brown, Red, Orange, Yellow, Green, Blue, Violet, Grey, White]
+}
+
+fn find_index(list: List(a), predicate: fn(a) -> Bool) -> Result(Int, Nil) {
+  find_index_loop(list, predicate, 0)
+}
+
+fn find_index_loop(
+  list: List(a),
+  predicate: fn(a) -> Bool,
+  index: Int,
+) -> Result(Int, Nil) {
+  case list {
+    [] -> Error(Nil)
+    [head, ..tail] ->
+      case predicate(head) {
+        True -> Ok(index)
+        False -> find_index_loop(tail, predicate, index + 1)
+      }
+  }
+}