Show HN: Fuse – statically typed functional programming language (fuselang.org)

It looks like a tidy little functional language - a small, easily grasped syntax surface and generally clear semantics. That you've got it to the point that it can compile and run proper programs is a great achievement for a solo dev project!

The string type in the standard library isn't Unicode-aware, might be worth just noting that. Unicode support can be a big undertaking, but considering whether you'll add it later or not might affect your library design now.

I don't really understand why you have an IO monad. The language isn't pure - `.exec()` means any function can perform IO actions no matter its type signature - so what's IO really for?

Do `impl` additions export? What happens when two libraries add the same function name with different signatures (or just bodies!) to a type's `impl` ?

Is currying automatic? It doesn't seem to be, but, eg, the `sum(x: i32, y: i32)` function theoretically could be called as `sum(5)` to create a closure, but this isn't a documented feature if so.

The website's font is using ligatures, not unicode operator symbols - I'd personally find it much clearer to use a non-ligature font to show what's really there, but that's immaterial to the language.

    trait Functor[A]:
      fun map[B](self, f: A -> B) -> Self[B];

    trait SizedFunctor[A]: Functor[A]:
      type Size;
      fun size(self) -> Size;

Relatedly, I want to read `Self` in there as ‘the thing that implements `Functor[A]`’ (e.g. List[A]`), but that makes `Self[B]`, instantiated, mean `List[A][B]`, which I think should be a kind error.

I know jShell has been here like 10 years, but I'm not sure it's convenient to quickly write to a file, query a url, etc.

.ksh for Kotlin? Typescript (through Deno)? Lua?

How expressive is fuse? How long are equivalent programs written in fuse/rust/scala/haskell?

Can you show me a bug that the fuse compiler catches but some or all of the competition doesn't?

From what I understand, GRIN does some parts of supercompilation [1] during optimization process. Supercompilation can prove equivalence of functional programs [2] modulo termination. So you can have something interesting and useful in almost no time. ;)

  [1] https://themonadreader.wordpress.com/wp-content/uploads/2014/04/super-final.pdf
  [2] https://www.researchgate.net/publication/225252220_Proving_the_Equivalence_of_Higher-Order_Terms_by_Means_of_Supercompilation