regexyl · December 9, 2023 09:48 · Dec 9, 2023 · Dec 9, 2023
diff --git a/aot-day8.ts b/aot-day8.ts
@@ -0,0 +1,33 @@
+// Filter out key-value pairs in an object that start with 'naughty'
+
+type RemoveNaughtyChildren<T extends {}> = {
+	[key in keyof T as key extends `naughty_${string}` ? never : key] : T[key]
+}
+
+// Test cases
+
+import { Expect, Equal } from 'type-testing';
+
+type SantasList = {
+  naughty_tom: { address: '1 candy cane lane' };
+  good_timmy: { address: '43 chocolate dr' };
+  naughty_trash: { address: '637 starlight way' };
+  naughty_candace: { address: '12 aurora' };
+};
+type test_wellBehaved_actual = RemoveNaughtyChildren<SantasList>;
+//   ^?
+type test_wellBehaved_expected = {
+  good_timmy: { address: '43 chocolate dr' };
+};
+type test_wellBehaved = Expect<Equal<test_wellBehaved_expected, test_wellBehaved_actual>>;
+
+type Unrelated = {
+  dont: 'cheat';
+  naughty_play: 'fair';
+};
+type test_Unrelated_actual = RemoveNaughtyChildren<Unrelated>;
+//   ^?
+type test_Unrelated_expected = {
+  dont: 'cheat';
+};
+type test_Unrelated = Expect<Equal<test_Unrelated_expected, test_Unrelated_actual>>;
diff --git a/day9.ts → aot-day9.ts b/day9.ts → aot-day9.ts
diff --git a/day9.ts b/day9.ts
@@ -0,0 +1,55 @@
+// Reverse a string
+
+type Reverse<S extends string> =
+  S extends `${infer First}${infer Rest}`
+    ? `${Reverse<Rest>}${First}`
+    : '';
+
+// Test cases
+
+import { Expect, Equal } from 'type-testing';
+
+type test_0_actual = Reverse<'rehsaD'>;
+//   ^?
+type test_0_expected = 'Dasher';
+type test_0 = Expect<Equal<test_0_expected, test_0_actual>>;
+
+type test_1_actual = Reverse<'recnaD'>;
+//   ^?
+type test_1_expected = 'Dancer';
+type test_1 = Expect<Equal<test_1_expected, test_1_actual>>;
+
+type test_2_actual = Reverse<'recnarP'>;
+//   ^?
+type test_2_expected = 'Prancer';
+type test_2 = Expect<Equal<test_2_expected, test_2_actual>>;
+
+type test_3_actual = Reverse<'nexiV'>;
+//   ^?
+type test_3_expected = 'Vixen';
+type test_3 = Expect<Equal<test_3_expected, test_3_actual>>;
+
+type test_4_actual = Reverse<'temoC'>;
+//   ^?
+type test_4_expected = 'Comet';
+type test_4 = Expect<Equal<test_4_expected, test_4_actual>>;
+
+type test_5_actual = Reverse<'dipuC'>;
+//   ^?
+type test_5_expected = 'Cupid';
+type test_5 = Expect<Equal<test_5_expected, test_5_actual>>;
+
+type test_6_actual = Reverse<'rennoD'>;
+//   ^?
+type test_6_expected = 'Donner';
+type test_6 = Expect<Equal<test_6_expected, test_6_actual>>;
+
+type test_7_actual = Reverse<'neztilB'>;
+//   ^?
+type test_7_expected = 'Blitzen';
+type test_7 = Expect<Equal<test_7_expected, test_7_actual>>;
+
+type test_8_actual = Reverse<'hploduR'>;
+//   ^?
+type test_8_expected = 'Rudolph';
+type test_8 = Expect<Equal<test_8_expected, test_8_actual>>;