Programming and thinking the functional way

It is at the core of many mobile to internet gateways out there. At the core of WhatsApp. Some databases (Riak, CouchDB) and message queues (RabbitMQ).

Language-wise, besides concurrency constructs, you get pattern matching, immutable data structures (and bindings). Unlike Haskell, all types are dynamic (but strong).

Also a counterpart to Learn You A Haskell For Great Good is Learn You Some Erlang For Great Good:

http://learnyousomeerlang.com/syntax-in-functions#pattern-ma...

For example the quicksort sample would look like:

    sort([Pivot|T]) ->
      sort([ X || X = Pivot]);

    sort([]) -> [].

  public class QS {
  	public List Quicksort(List l, Comparator comp) {
  		if (l.size()  lesser = new ArrayList();
  		List greater = new ArrayList();
  		
  		T pivot = l.get(0);
  		
  		for (T t: l) {
  			if (comp.compare(pivot, t)  out = new ArrayList();
  		out.addAll(Quicksort(lesser));
  		out.addAll(Quicksort(greater));
  		
  		return out;
  	}
  }

I don't think this is a fair comment considering the in-place Haskell implementation isn't incredibly readable either.

1) If it's simple to imagine the computer doing something, it should be easy to program.

2) If it's simple to analyze something mathematically, it should be easy to program.

The first path leads to C-style programming with pointers and loops. The second path leads to lazy pure functional programming and beyond.

Personally, I'm in the first camp. Small functional programs are often shorter and more beautiful than their imperative and OO counterparts, but large functional programs quickly accumulate so many abstractions that they become incomprehensible to me, more so than large imperative or OO programs.

Maybe that just says something about my intelligence, or maybe the functional camp hasn't yet figured out how to write large programs in a readable way. Case in point, see the list of operators defined by the popular Lens library in Haskell: http://hackage.haskell.org/package/lens-3.8.5/docs/Control-L...