[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.

[mr_custard]

> 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.

F# is also a member of the ML family and is totally fit for production.

[FridgeSeal]

F# is the language I want to like, and would like to use in prod, but it constantly feels like the ignored step-child.

The REPL is great in theory, but trying to import packages is a nightmare every time I try.

Dependencies exist, but they all seem to target wide and inconsistent range of the ecosystem. Want to target dotnetcore 3.1? Good luck have fun: everything you find useful is targeting some combination of standard/framework/core/whatever confusing variant Microsoft decides to come up with this week.

If I somehow convinced my co-workers to adopt a language that wasn't C#, I'd point them Rust or Haskell instead.

[akra]

Most of those package issues also apply to C# particularly as it stabilizes towards .NET 5. However it isn't too bad once you get it; and for most standard use cases it seems to work with the dotnet cli out of the box. Many people seem to be productive with C# so I'm not sure how big of an issue it is other than the small initial learning curve but many package managers have that (IMO Maven is harder yet many people use that in Java space and not too hard once you learn it).

REPL's often have problems with package management in a number of languages as they often have a different build chain from the compiled style apps which have the chance to resolve packages. When doing .NET Core in the past I know Paket can generate these scripts for the REPL to import packages (seen csx/fsx scripts for each package) - but another comment alludes to a more supported way in the future which is good.

Doesn't seem like you have a problem with the language per se; rather the package management story for .NET Core.

[Paradigma11]

I totally agree with your points but the situation seems to be improving. With https://devblogs.microsoft.com/dotnet/announcing-f-5-preview... you can import nuget packages in fsx scripts. The dependency situation also seems to grow saner every month.

Nevertheless i would still wait another few month for things to stabilize with .net 5.

[tombert]

I think that F# is ok for production. I used it at a previous job without too many pain-points, especially in comparison to Haskell. I'm not a huge fan of MSBuild, but it works relatively well, and of course you have access to the massive .NET library and the entire ecosystem of C# libraries out there, and there's even some tooling to make the C# stuff play nicely with the F# constructs.

[tome]

I totally forgot F# was part of the ML family, but can't edit my comment now! Thanks to everyone who replied to correct me.

[_bxg1]

There's ReasonML, which compiles to JS and seems intended for production

[tomku]

Reason is a syntax layer on top of OCaml, so it shares OCaml's production-readiness. The tooling that Reason uses to compile to JS (Bucklescript) was originally designed for OCaml, and Reason supports native targeting via the plain OCaml compiler backend as well. It's a pretty pleasant ecosystem at the moment.

[kqr]

In the same space we also find Fable, which hooks into Babel to compile F# to JS. We're using it in production and it's been surprisingly good. It's very nice to be able to share the definitions of data structures between the C# backend and JS (via F#) front-end.

[smabie]

ReasonML serves no purpose whatsoever. The syntax is worse than OCaml's (though, more regular) and the editor tooling is really awful. OCaml compiles to JS just fine.

[ska80]

Idris 2 is a big step towards a production grade FP language