Haskell makes it so easy to write correct concurrent code it's not even funny. GHC's magnificent IO manager means I can handle 1000s of connections on one amazon instance. Can't understand why you wouldn't be using Haskell for server-side web development.

No other popular server-side language supports concurrency (see STM, MVar's, and Chans), transparent futures/promises for I/O (the entire IO monad in GHC is non-blocking), support for multiple processors (Just add +RTS -N<n> to make your program scale to n processors), and a blazing fast HTTP server (warp).

I can't tell whether that's just a rhetorical flourish, so I'll answer straight.

To begin with, there are a couple of concerns that might kill an attempt to use Haskell.

1. I might not be able to get management approval. Haskell is an obscure language with a reputation for difficulty. The bosses might well say no. 2. I might need to work with an existing codebase in something like Java or Python. Not possible from Haskell.

If those don't kill the project, there's the cost-benefit tradeoff. On the benefits side: 1. Haskell code is very concise. (definitely) And greater concision means faster development. (possibly) 2. Haskell code is less likely to contain errors, because of very strict typing. (probably) 3. Haskell coders are disproportionately capable, because the language is obscure and difficult. (probably)

On the costs side: 1. I have much more experience in other languages. It would take at least a year, maybe two before I'd be up to pro standards in Haskell. 2. The community of Haskell programmers is small. It might be difficult to hire anyone if the project grew; I might be faced with training someone from scratch, not just in a new language, but in a new programming paradigm.

So, this isn't anything like a slam dunk. Quite the opposite, actually. There are a couple of issues that might nix the project right up front, and then a daunting cost-benefit calculation.

Your second one will take longer than it would have in PHP or J2EE or whatever else you're used to building web stuff in. It will, like the first, also be ugly but unlike the first project will eventually work. It'll also fall over catastrophically early on, but will be salvageable. Once past its initial deployment/perf issues, it'll sit and hum away quietly in a corner with much less care and feeding than traditional web technologies. (Though you'll keep wanting to go back to it, because it's more fun to work in that than whatever else you're working on)

The third production Haskell project will come together much more quickly. Unfortunately, by this time you'll probably be bringing other people on and this will be their first big Haskell project. (See above about what happens to first big Haskell projects) So the parts delegated to other programmers will fail to work, and there will need to be lots of hand-holding and discussion of type design at first.

Selling management on this is indeed difficult. I'll admit that I'm still not clear on how we sold the first (failed) project to management or how I convinced my boss to let me use Haskell a second time. I mean, I was there, but I don't know how I did it.

[0] as in people/social/management issues

[0] http://elixir-lang.org/docs/v1.1/elixir/Task.html

[1] https://github.com/ninenines/cowboy

I think right now the lack of educational materials and overall difficulty of learning it make it impractical for industry use unless you plan on only having a very small team. I don't know what 10% you are referring to but I personally find performance analysis to be a huge issue due to the laziness. I suspect this is largely due to the lack of educational materials which is why I'm a little skeptical that the release of one book will suddenly make it all okay as the article seems to suggest.

Still, I find the language itself a complete joy to use and use it almost wherever I can.

It already is. If you are talking about a full stack web application, there are several fully featured production quality frameworks, Yesod being the most popular.

What are the negatives to you? Long compile times? Monadic IO? Memory leaks from lazy eval?

Compiling to JavaScript is totally okay if the new language 1) adds something meaningful (like a type system [TypeScript, js_of_ocaml] or the ability to conveniently deal with unboxed data [LLJS, Emscripten]) and 2) does not have a significant runtime overhead. GHCJS, in particular, adds a _huge_ amount of runtime overhead, largely because JavaScript doesn't (yet) support tail calls so the CPS transform must be trampolined. In addition, laziness doesn't make a lot of sense for frontend code, which generally should be as tight as possible. Also, look at the code produced by ScalaJS sometime and weep. :D

js_of_ocaml, on the other hand, produces extremely tight code, and is very suitable for building web frontends. Of course, OCaml probably has a similar learning curve as Haskell. I can't imagine people would get excited about the syntax.

TypeScript is a sweet spot: it's got some value over straight up ES6, but it's easy to integrate and has a very short learning curve.

I wonder if any research has been done here as to "let the stack grow" and THEN trampoline before it overflows.

Aside from the solid compiler ghc and many libraries, the ability to write less, more reliable software. That's the objective isn't it?

Another reason is the increasing number of usable languages written in Haskell. Using say Purescript, elm or other front-end languages, it may be as important as knowing Haskell as know C is for Python, for example.

For us older engineers, full-stack was hardware up to OS up to apps. Quite a few projects did that. Haskell is more full stack via that definition given it can build hardware (Bluespec), OS's (House), system code (Ivory), and web apps. Worst case, use it as a DSL to output the language of your choosing like 4GL's used to.

We're using Haskell for server-side programming at my work and it's been fantastic. Functional programming is so well suited for stateless web services.