[the_af]

> A bit off topic, but is Haskell viable for production? Or is it just really intended as an experiment?

It's viable for production and there are businesses which use it, notably fintechs. Also Facebook for some things (Facebook employs Simon Marlow [1]). And I know this is an irrelevant anecdote, but I have a friend who has been working in several startups which use Haskell for the last few years. Like Paul Graham has argued of Lisp, Haskell really is a "secret weapon" and people who use it for production tend to love it.

EDIT: a prior version of this post claimed Facebook employed Philip Wadler, which is incorrect. Sorry! I got my wires crossed and confused Philip Wadler with Simon Marlow!

[1] https://www.linkedin.com/in/simonmarlow/

[nextos]

> Haskell really is a "secret weapon" and people who use it for production tend to love it

That's exactly my question. I'd be really interested in hearing about domains where Haskell is a secret weapon and how it compares to ML family languages and dependently-typed ones.

[implicit]

I did a bunch of professional Haskell work in a prior life[1]. Most of its 'secret weapon' status springs from the way Haskell lets you control side effects.

We had a fantastic unit testing harness[2]. With effect tracking, you can arrange for your harness to put precise fences around nondeterministic code. You don't need to rely on experience and discipline to ensure that tests are reliable or fast. The type system does it for you.

Effect tracking also makes concurrent code easier to write. You have a great deal of control over how and when threads can be created, and what kinds of logic is permitted on those threads.

GHC's IO manager offers green threads and async IO, so rather than a select loop, you just fork threads and perform "blocking" IO calls. You get about the same efficiency as a select loop this way.

Lastly, something we learned to appreciate over the years is that Haskell is easier to refactor. When you combine the rigid type system, effect tracking system, and ease of writing unit tests, it becomes very easy to refactor old Haskell. It doesn't really matter how bad the old code was or whether the original author is around to help you at all.

If you intend for your product to evolve continuously forever, this is truly a secret weapon.

    [1] https://andyfriesen.com/2014/03/25/what-its-like-to-use-haskell.html
    [2] https://andyfriesen.com/2015/06/17/testable-io-in-haskell.html

[6gvONxR4sf7o]

Of all the things I like in haskell (having only used it a as a hobbyist), refactoring tops the list. It's a lot less scary to refactor when the compiler tells you so much about which parts you missed.

[ghostwriter]

https://news.ycombinator.com/item?id=23367803

[the_af]

I'll let people who actually use it -- instead of toy with it, like myself -- answer you. I know many haskellers read HN and have answered similar questions in the past.

Like I said, I do know Haskell is used at fintechs (source: a friend whose job is precisely that).

[auggierose]

Facebook employs Wadler? Since when?

[the_af]

Gah! I meant to say Simon Marlow [1], co-developer of the Glasgow Haskell Compiler (GHC) [2]. Sorry for the confusion, I'll edit my other post now.

  [1] https://www.linkedin.com/in/simonmarlow
  [2] https://en.wikipedia.org/wiki/Simon_Marlow