Show HN: Fluent, tiny lang for reactivity and autograd

#1

Post by mlajtos » Fri, Jul 17, 2026, 7:50 PM UTC

After six months of work, I am here again presenting Fluent – a tiny lang which is optimized for differentiable & reactive programming.

Since I am not Conal Elliot, don't expect a beautiful theoretical unification of FRP and AD from first principles. Rather, a horrific monster that holds together mostly because a lot of duct-tape.

The link points to the semi-interactive tour of the language, which will get the job done much better than I could in here.

Hope you hate/like it!

Show HN: Fluent, tiny lang for reactivity and autograd
mlajtos.github.io

Re: Show HN: Fluent, tiny lang for reactivity and autograd

#2

Post by sightspinner » Fri, Jul 17, 2026, 9:07 PM UTC

Was this just for fun/practice or are you trying to solve some problem/do something more efficiently? Surely, there are languages the calculate exact derivatives already?

Re: Show HN: Fluent, tiny lang for reactivity and autograd

#3

Post by mlajtos » Fri, Jul 17, 2026, 10:16 PM UTC

sightspinner wrote: post #2

Was this just for fun/practice or are you trying to solve some problem/do something more efficiently? Surely, there are languages the calculate exact derivatives already?

Fluent is attacking multiple problems.

On the surface, it blends APL and LISP. Making S/M-exprs terse and building “diamond-less” left-to-right APL on top. This part is pretty okay.

In core, unification of FRP and AD as already mentioned. This is mainly to do efficient online/incremental learning. Currently this is a disaster and main source of tech debt. I got some attacks.

Fun and curiosity is the main motivator. Having single system that can do user-editable explorable ML explanations is just cherry on top.