[Haskell-cafe] What is your favourite Haskell "aha" moment?

[Tom Ellis]

On Sat, Jul 14, 2018 at 10:17:43AM +0300, Paul wrote:
> > Once the FSM holds more than a dozen states, these advantages evaporate.
>
> This is point only where I can not agree.  I used FSM with hundreds
> states/transitions.  It was automatically generated, I only check them. 
> Also I know that in car automatics FSM are widely used (BMW, Mercedes,
> Audi).  Also it’s using in software for space industry widely.  My IMHO
> is: FSM is most reliable way to do soft without bugs.  Also it’s easy to
> verify them (for example, with transitions’ assertions)

It's interesting to see all this chat about FSMs, when FSMs are essentially
"just" a tail recursive function on a sum type.