sasajib · November 15, 2023 15:18 · Nov 15, 2023
diff --git a/either.ts b/either.ts
@@ -0,0 +1,41 @@
+export class Either<L, R> {
+  constructor(private left: L | null, private right: R | null) {}
+
+  static left<L, R>(value: L): Either<L, R> {
+    return new Either<L, R>(value, null);
+  }
+
+  static right<L, R>(value: R): Either<L, R> {
+    return new Either<L, R>(null, value);
+  }
+
+  isLeft(): boolean {
+    return this.left !== null;
+  }
+
+  isRight(): boolean {
+    return this.right !== null;
+  }
+
+  getLeft(): L {
+    if (this.isLeft()) {
+      return this.left as L;
+    }
+    throw new Error("Attempted to get Left value from a Right");
+  }
+
+  getRight(): R {
+    if (this.isRight()) {
+      return this.right as R;
+    }
+    throw new Error("Attempted to get Right value from a Left");
+  }
+
+  map<T>(f: (right: R) => T): Either<L, T> {
+    if (this.isRight()) {
+      return Either.right<L, T>(f(this.getRight()));
+    } else {
+      return Either.left<L, T>(this.getLeft() as L);
+    }
+  }
+}