[bjz_]

> OCaml's is also excellent but not immediately obvious (their docs have improved a lot)

Interesting! The last time I tried OPAM, it actually seemed more frustrating than Cabal! Maybe it's improved? Last time I tried OPAM it would install packages globally by default, and avoiding that was a confusing process, when that should be the default behavior.

Cargo (while not perfect) has really nice defaults out of the box - ie. it generates a lockfile by default, scopes packages locally to individual projects, and lets you use more than one package of the same version in the same project.

Really hoping OCaml and Haskell can improve their package management story - they are getting there, but it still holds me back from really using them on a daily basis.

[nextos]

A bit off topic, but is Haskell viable for production? Or is it just really intended as an experiment? Is it worthwhile to jump into Haskell now, or perhaps one should look into Idris or Agda? Any companies using Haskell where it has proven a distinct advantage?

Ocaml and SML (the former being sadly quite unpopular these days) are an order of magnitude simpler than Haskell. They are easy to master. I have been quite productive with Scala which, while being a member of the ML family, is much more intricate due to OO + FP on top of great Java interop and many Haskell-like features (laziness, monads, lenses...).

Haskell doesn't feel the same. I have learned some Haskell over the years. Since I come from a pure FP education (started with SML) and I have lots of type theory background, everything feels familiar, yet I've found it really hard to be productive or to justify the mental overhead of laziness. I have developed some small projects in Haskell, but I haven't found it a productive alternative to the languages above.

[bojo]

My company writes and supports a lot of custom Haskell software for our parent, an ISP up in Alaska.

What we gain is a high level of confidence in our business logic rules due to strict typing, fewer overall tests, and by avoiding a few small gotchas uncrashable runtimes.

Not to say it doesn’t come without problems. Poor IDE integration (I personally don’t care), questionable documentation at times, and a steep rewrite your brain learning curve.

Some posts I have written.

https://www.alasconnect.com/2018/10/02/introducing-haskell-c...

https://www.alasconnect.com/2018/10/04/productive-haskell-en...

http://blog.bojo.wtf/2020/04/15/is-haskell-a-bad-choice/

[MaxGabriel]

I'm the CTO at Mercury (https://mercury.com/) and we have 100% of our backend written in Haskell. It's gone really well so far.

Answering another commenter's question, I would say the "secret weapons" are:

1. Hiring: Haskell is a very in-demand language by very good engineers. For a startup, it's absolutely amazing for recruiting and I can't overstate how important recruiting good people is for a startup.

2. Correctness: Haskell helps you ensure your code doesn't have bugs. For a bank this is fairly important. Some aspects of Haskell that are great for this: algebraic data types ("discriminated unions" in some languages) model business logic quite well, purity makes a function much more of a known quantity, libraries like Persistent ensure type-safe SQL queries, and in general the community cares about correctness.

I haven't used the other languages you mentioned, so I can't really speak to a comparison with them. Re: laziness, it's almost never something I think about in practice.

[tome]

To answer your questions literally without much nuance:

Yes, Haskell is viable for production. There are caveats, as with any other language. Haskell has more caveats that most other languages you would be familiar, but it's nonetheless perfectly suitable in the right environment.

No, don't use Agda or Idris in production, they're totally unfit. Agda is not intended to be. Idris may be but it will take 5 or 10 years.

The only members of the ML family that I'm aware of are Ocaml and the flavours of Standard ML. Only Ocaml is fit for production.

[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/

[alephu5]

I've got a REST API in production linking to postgres and rabbitmq and I'm very happy with the performance and maintainability. The ecosystem is a bit more bare than with other languages like node, python or java but in exchange the paradigm and type-system lets you build safe and well isolated code. In my opinion it's also quite easy to read despite being terse.

Despite the complaints the build tooling is good, and there are decent plugins for IDE capabilities although they're a little bit resource hungry.

My biggest problem is the lack of component libraries, for example I wanted to use SMTP a little while ago but couldn't find a library compatible with the latest GHC so ended up writing a python script connected to rabbitmq.

For business logic involving timezones, currencies, API calls, calculations etc. you're pretty well covered though.

[embwbam]

I’ve used it on multiple projects for clients over the last 5 years. These projects were large, made it to production, and were successful. I love it. Once you clear the initial learning curve it feels very productive, and gives you the feeling of always having something more to learn and master.

[hazz99]

Hasura (one of my favourite technologies) is built with Haskell!

[ghostwriter]

> Really hoping OCaml and Haskell can improve their package management story - they are getting there, but it still holds me back from really using them on a daily basis.

Cabal 3.x with Nix-style buildscovers all packaging needs that I ever had with Haskell ecosystem[1]. And there's a new wave of tooling based on incremental Nix builds, that you can begin using today [2]

[1] https://cabal.readthedocs.io/en/latest/nix-local-build-overv...

[2] https://github.com/nmattia/snack

[bjz_]

Yeah, it's really great to see the progress there. However, afaik, it still doesn't freeze packages by default, or let you have multiple packages of the same version in a dependency tree[1]. The former can be worked around, but it's annoying that it's not the default. The latter is more frustrating however!

[1] https://news.ycombinator.com/item?id=23454711

[marcosdumay]

Yep. Cabal 3.x is great, better than anything else I've seen for any other language.

As the article says, it just needs to correct the default behavior (deprecating the old behavior is on the roadmap, interestingly, the documentation doesn't even say what is the standard right now) and some improvements on usability (just better docs goes a long way).

[talex5]

By default, opam installs everything into the current "switch". Typically you have switch one per compiler, but you can create one per project. You can also create a "local" switch directly inside your project directory: https://opam.ocaml.org/blog/opam-local-switches/

Another option is to use the duniverse tool (https://github.com/ocamllabs/duniverse). That downloads all dependencies to the project directory, and then builds them all together as one giant project. That makes it very easy to make changes across multiple libraries at once, while keeping fast incremental builds.

And a final option is to build projects with Docker, which allows you to have separate versions of non-OCaml packages too.

[bjz_]

Ahh cool - had some similar questions here: https://news.ycombinator.com/item?id=23460980 - mainly, how much manual switching do you have to do? Or is it seamless, depending on what project directory your in? I think I tried the local switches in the past and got really confused when switching projects and everything broke, thinking 'wasn't all this meant to prevent this?'.

[Erlangen]

Packages are not installed globally in opam by default nowadays. `opam switch` "enables the user to have several installations on disk, each with their own prefix, set of installed packages, compiler version, etc". https://opam.ocaml.org/doc/Usage.html#opam-switch

[bjz_]

Oh that's nice to hear! Some questions:

Do you have to run this command manually, and does it mutate the shell state? That's one thing that frustrated me with opam in the past as well. I couldn't just jump into a directory and build a thing, then switch to another project directory - there was a lot of manual switching and unswitching of packages if I recall correct?

Is it possible to install multiple tools globally using opam that use disjoint library versions? Like, I might want to install Abella and Coq side-by-side, but they might have conflicting version requirements. I think I was super excited about opam 2, then tried installing one thing, only to have it break again when I installed something else.

Is it possible to have multiple versions of the same libray in the same project, or does the constraint solver need to find a single solution for each library? [1]

[1] https://news.ycombinator.com/item?id=23454917

[pdimitar]

I got told some months ago to look for these docs: https://news.ycombinator.com/item?id=22395595

It seems all we want can be made to work but it does require some tinkering and being aware of the tools' options.

[andrepd]

Maybe you tried it before v2? Imho opam now is very usable, lets you be productive for 95% tasks after reading a 5min introduction, and generally gets out of your way.