X Option

Option : a safe, eager Optional type

Creating Options

some : Some represents a value that is present

Option.some(10) //Some[10]

none : None represents the absence of a value

Option.none() //None[]

The JDK has Optional, which suffers from a number of flaws which are not present in cyclops X's Option type.

1. Optional::get - throws a NoSuchElementException when called on Optional::empty
2. Null is not a valid value : java Optional.of(10).map(i->null) results in Optional.empty rather than Optional[null]

1. Optional::get / Option::getOrElse

Cyclops Option does not provide a direct get method, instead overloads are provided where users can provide a default value as an alternative. E.g.

Option.some(10)
      .orElse(-10);

Option.some(10)
      .orElseGet(()->-10);

Another alternative is to use a fold, which takes a Function and a Supplier. The Function is executed when a value is present in the Option (the input parameter is the value), the Supplier is called when no value is present.

Option.some(10)
      .fold(i->i+5,()->-1); //15


Option.none()
      .fold(i->i+5,()->-1); //-1

2. Null is not a valid value

Not allowing Optional to store null introduces a special case within Optionals behaviour which breaks the generalized behaviour (as defined in the Monad laws) present in most other Optional / Option implementations. This may cause problems when using Optional with APIs where null is a valid value, the code below results in a RuntimeException.

Optional.of(null);

In cyclops null is a valid value for an Option.some instance. The code below does not throw any Exception

Option.some(null);

Like with Optional, conditional conversion of nullable values to Option.some / Option.none instances can be done via

Option.ofNullable(nullableValue);