diff --git a/alter.ts b/alter.ts
index b5f3d69..5d348bb 100644
--- a/alter.ts
+++ b/alter.ts
@@ -8,10 +8,11 @@
  * @example
  *
  * ```ts
+ * import { assertThrows } from "@std/assert";
  * import { alter } from "@core/errorutil/alter";
  *
  * console.log(alter(() => 1, "err2")); // 1
- * console.log(alter(() => { throw "err1" }, "err2")); // "err2" is thrown
+ * assertThrows(() => alter(() => { throw "err1" }, "err2"), "err2"); // "err2" is thrown
  * ```
  */
 export function alter<T, E>(fn: () => T, alt: E): T {
diff --git a/alter_else.ts b/alter_else.ts
index 9c6219c..9077bca 100644
--- a/alter_else.ts
+++ b/alter_else.ts
@@ -8,10 +8,11 @@
  * @example
  *
  * ```ts
+ * import { assertThrows } from "@std/assert";
  * import { alterElse } from "@core/errorutil/alter-else";
  *
  * console.log(alterElse(() => 1, () => "err")); // 1
- * console.log(alterElse(() => { throw "err" }, (err) => "new " + err)); // "new err" is thrown
+ * assertThrows(() => alterElse(() => { throw "err" }, (err) => "new " + err), "new err"); // "new err" is thrown
  * ```
  */
 export function alterElse<T, E>(fn: () => T, elseFn: (err: unknown) => E): T {
diff --git a/attempt.ts b/attempt.ts
index 56fc3ea..e7b3098 100644
--- a/attempt.ts
+++ b/attempt.ts
@@ -16,10 +16,10 @@ export type Result<T, E> = Success<T> | Failure<E>;
  * console.log(attempt(() => { throw "err" })); // ["err", undefined]
  * ```
  */
-export function attempt<T, E>(fn: () => T): Result<T, E> {
+export function attempt<T, E = unknown>(fn: () => T): Result<T, E> {
   try {
     return [undefined, fn()];
   } catch (e) {
-    return [e, undefined];
+    return [e as E, undefined];
   }
 }
diff --git a/mod.ts b/mod.ts
index 3eed553..1088c23 100644
--- a/mod.ts
+++ b/mod.ts
@@ -1,3 +1,5 @@
+export * from "./alter.ts";
+export * from "./alter_else.ts";
 export * from "./attempt.ts";
 export * from "./error_object.ts";
 export * from "./raise.ts";