Add bind() to option and result

src/Option.php

@@ -93,6 +93,21 @@ readonly class Option
         return $this->value ?? $f();
     }
 
+    /**
+     * Bind a function to this option (railway processing)
+     *
+     * If this option is Some, the function will be called with the option's value. If this option is None, it will be
+     * immediately returned.
+     *
+     * @template TBound The type returned by Some in the bound function
+     * @param callable(T): Option<TBound> $f The function that will receive the Some value; can return a different type
+     * @return Option<TBound> The updated option if the starting value was Some, None otherwise
+     */
+    public function bind(callable $f): Option
+    {
+        return $this->isNone() ? $this : $f($this->get());
+    }
+
     /**
      * Map this optional value to another value
      *

src/Result.php

@@ -87,6 +87,22 @@ readonly class Result
         return $this->errorValue->isSome();
     }
 
+    /**
+     * Bind a function to this result (railway processing)
+     *
+     * If this result is OK, the function will be called with the OK value of the result. If this result is Error, it
+     * will be immediately returned. This allows for a sequence of functions to proceed on the happy path (OK all the
+     * way), or be shunted off to the exit ramp once an error occurs.
+     *
+     * @template TBoundOK The type returned by OK in the bound function
+     * @param callable(TOK): Result<TBoundOK, TError> $f The function that will receive the OK value; can return a different type
+     * @return Result<TBoundOK, TError> The updated result if the function was successful, an error otherwise
+     */
+    public function bind(callable $f): Result
+    {
+        return $this->isError() ? $this : $f($this->getOK());
+    }
+
     /**
      * Map an `OK` result to another, leaving an `Error` result unmodified
      *