feat: adds transpose

README.md

@@ -23,6 +23,7 @@ Heavily inspired by rust [std::option](https://doc.rust-lang.org/std/option/inde
       - [okOrElse](#okOrElse)
       - [or](#or)
       - [orElse](#orElse)
+      - [transpose](#transpose)
       - [xor](#xor)
       - [unwrap](#unwrap)
       - [unwrapOr](#unwrapOr)
@@ -202,6 +203,14 @@ Some(10).orElse(() => 1000) // Some(10)
 None().orElse(() => 1000) // Some(1000)
 ```
 
+#### transpose
+
+Transposes an `Option` of a `Result` into a `Result` of an `Option`.
+
+```ts
+Option(100).transpose() // Ok(Some(100))
+```
+
 #### xor
 
 Returns Some if exactly one of self, optb is Some, otherwise returns None.

src/Option.ts

@@ -262,6 +262,20 @@ class OptionLike<T> {
     return this.isSome() ? this : f();
   }
 
+  /**
+   * Transposes an `Option` of a `Result` into a `Result` of an `Option`.
+   *
+   * ```ts
+   * Option(100).transpose() // Ok(Some(100))
+   * ```
+   *
+   * @returns {(Ok<Some<T>> | Ok<None>)}
+   * @memberof OptionLike
+   */
+  public transpose(): Ok<Some<T>> | Ok<None> {
+    return this.isSome() ? Ok(Some(this.value)) : Ok(None());
+  }
+
   /**
    * Returns Some if exactly one of self,
    * optb is Some,

src/__tests__/Option.spec.ts

@@ -113,4 +113,9 @@ describe(`Option`, () => {
     expect(Some(100).okOrElse(() => Err("foo"))).toStrictEqual(Ok(100));
     expect(None().okOrElse(() => Err("foo"))).toStrictEqual(Err("foo"));
   });
+
+  it("Transposes an `Option` of a `Result` into a `Result` of an `Option`.", () => {
+    expect(Some(100).transpose()).toStrictEqual(Ok(Some(100)));
+    expect(None().transpose()).toStrictEqual(Ok(None()));
+  });
 });