Add contains, exists, toArray

- Update docs

src/Result.php

@@ -103,12 +103,38 @@ readonly class Result
         return $this->isError() ? $this : $f($this->getOK());
     }
 
+    /**
+     * Does this result's "OK" value match the given value?
+     *
+     * @param TOK $value The value to be matched
+     * @param bool $strict True for strict equality (`===`), false for loose equality (`==`); optional, default is true
+     * @return bool True if the "OK" value matches the one provided, false otherwise
+     */
+    public function contains(mixed $value, bool $strict = true): bool
+    {
+        return match (true) {
+            $this->isError() => false,
+            default          => $this->okValue->contains($value, $strict),
+        };
+    }
+
+    /**
+     * Does the "OK" value of this result match the given predicate function?
+     *
+     * @param callable(TOK): bool $f The function to determine whether the value matches
+     * @return bool True if the OK value matches the function, false otherwise
+     */
+    public function exists(callable $f): bool
+    {
+        return $this->isOK() ? $f($this->okValue->get()) : false;
+    }
+
     /**
      * Map an `OK` result to another, leaving an `Error` result unmodified
      *
-     * @template U The type of the mapping function
-     * @param callable(TOK): U $f The mapping function
-     * @return Result<U, TError> A transformed `OK` instance or the original `Error` instance
+     * @template TMapped The type of the mapping function
+     * @param callable(TOK): TMapped $f The mapping function
+     * @return Result<TMapped, TError> A transformed `OK` instance or the original `Error` instance
      */
     public function map(callable $f): self
     {
@@ -118,9 +144,9 @@ readonly class Result
     /**
      * Map an `Error` result to another, leaving an `OK` result unmodified
      *
-     * @template U The type of the mapping function
-     * @param callable(TError): U $f The mapping function
-     * @return Result<TOK, U> A transformed `Error` instance or the original `OK` instance
+     * @template TMapped The type of the mapping function
+     * @param callable(TError): TMapped $f The mapping function
+     * @return Result<TOK, TMapped> A transformed `Error` instance or the original `OK` instance
      */
     public function mapError(callable $f): self
     {
@@ -139,6 +165,16 @@ readonly class Result
         }
     }
 
+    /**
+     * Convert this result into a 0 or 1 item array
+     *
+     * @return TOK[] An empty array for `Error`, a 1-item array for `OK`
+     */
+    public function toArray(): array
+    {
+        return $this->okValue->toArray();
+    }
+
     /**
      * Transform a `Result`'s `OK` value to an `Option`
      *