LunarML – Standard ML compiler that produces Lua/JavaScript

I've had a great time discovering Fable, which compiles F# to JS or TS.

The cost of moving from VSCode to neovim has always put me off, but if I could write the config in F# it would tempt me more.

How far is standard ML from F#?

Is there any existing compiler for F# => Lua?

Is there any reason to use SML instead of OCaml in 2024?

Standard ML is pretty simple and easy to pick up, but a weak point is the lack of { record with updatedValue } syntax to create a new record which is the same as an existing one but with some value changed. You have to specify every field in the record which can be a pain depending on how large your record is.

Standard ML has some nice features though and I think what I mentioned is the only serious shortcoming (except for ecosystem if that's important to you).

Standard ML is also structurally (but strongly) typed, unlike F# and the vast majority of nominally typed languages, which is rare but nice.

type person = { age : int, name : string }

is the same as the type

type animal = { age : int, name = string }

but this hasn't been an issue foe me, and structural typing means you can avoid defining the type at all which is convenient for small records.

For example, a function to increment age has no need for you to define the type.

fun grow { name, age } = { name = name, age = age + 1 }

I think Standard ML helps you understand the origin of some common FP idioms. Like tuples are really just records and SML treats them as such. The empty record {} is the same as the empty tuple (): both are the unit type. And a record like { 1 : "a", 2 : "b" } is exactly the same as the tuple ("a", "b").

Not in production.

As an F# newbie, I hit some incompatibility early on with my initial library choices. Not everything works in fable. When I found Safe Stack, that went away.

Then it was great. Hot reload; generated js is passable; I'm doing front end in F# with zero JS and almost no html.

StandardML is the most practical functional programming language IMO. It concedes that mutation improves performance, laziness is hard for humans to optimize, and side effects exist. At the same time, it has avoided the weirdness of Ocaml or the unnecessary complexity of F#.

It's use of structural typing (like Typescript) rather than nominal typing is great. It winds up feeling a lot like a scripting language, but with better type safety than most non-scripting languages. The CML (concurrent ML) proposals are also much more mathematically grounded, consistent, and nice to use compared to most other languages.