Alternative Value Monads are all monadic types that can have an alternative value! What does this mean?
Well, it's best to start with Either<L, R>
(Left and Right). If first we think about a tuple:
(int, string)
This type can represent an int
AND a string
. Either
is it's natural 'dual', it can be an int
OR a string
:
Either<int, string>
In the case of Either
the Right value is considered the bound value of the monad, and the Left value is considered
the alternative value. All of the other alternative value monads can be seen as derivatives of Either
.
Type | Bound Value Type | Alternative Value Type |
---|---|---|
Option<A> |
A |
None |
Fin<A> |
A |
Error |
Fin<A> |
A |
Error |
Validation<F, S> |
S |
Seq<F> |
Validation<MonoidF, F, S> |
S |
F |
Nullable<A> |
A |
null |
Some<A> |
A |
ValueIsNoneException |
The alternative value is usually used to carry errors, but that doesn't have to be the case