2 files changed, 4 insertions, 3 deletions
diff --git a/u/fn/either.ts b/u/fn/either.ts
index 9dc1027..8b233bf 100644
--- a/u/fn/either.ts
+++ b/u/fn/either.ts
@@ -10,7 +10,7 @@ export interface IEither<E, T> {
     errBranch: Mapper<E, Ee>,
     okBranch: Mapper<T, Tt>,
   ) => IEither<Ee, Tt>;
-  fold: <Tt>(folder: BiMapper<E | null, T | null, Tt>) => Tt;
+  fold: <Tt>(folder: BiMapper<E | undefined, T | undefined, Tt>) => Tt;
   moveRight: <Tt>(t: Tt) => IEither<E, Tt>;
   mapRight: <Tt>(mapper: Mapper<T, Tt>) => IEither<E, Tt>;
   mapLeft: <Ee>(mapper: Mapper<E, Ee>) => IEither<Ee, T>;
@@ -31,8 +31,8 @@ export class Either<E, T> implements IEither<E, T> {
     return this.mapRight(() => t);
   }
 
-  public fold<R>(folder: BiMapper<E | null, T | null, R>): R {
-    return folder(this.err ?? null, this.ok ?? null);
+  public fold<R>(folder: BiMapper<E | undefined, T | undefined, R>): R {
+    return folder(this.err ?? undefined, this.ok ?? undefined);
   }
 
   public mapBoth<Ee, Tt>(
diff --git a/u/fn/mod.ts b/u/fn/mod.ts
index f0fbe88..265c6db 100644
--- a/u/fn/mod.ts
+++ b/u/fn/mod.ts
@@ -1,2 +1,3 @@
 export * from "./callable.ts";
 export * from "./either.ts";
+export * from "./memoize.ts";