OO design patterns vs FP idioms in Java 8

[Esko Luontola]

Victor Nazarov wrote on 3.10.2013 12:08:
> I've always percept Visitor-pattern as an implementation of Algebraic Data
> Types in Java-like languages. Visitor-pattern is just an implementation of
> pattern-matching on ADT-constructors, and this is already present as
> language-level feature in all ML-like languages (including Haskell).

Me too. I've implemented an actor framework (http://jumi.fi/actors.html) 
that relies on the Visitor pattern*; because Java doesn't have pattern 
matching, the natural way of receiving messages is by implementing an 
interface.

* Or maybe the Visitor pattern emerges from the use of Event Sourcing 
and this actor framework; the system that uses those actors is based on 
Event Sourcing, so in the UI layer visitors are needed to calculate the 
system state from the events.

-- 
Esko Luontola
www.orfjackal.net