Reminds me of http://lambda-the-ultimate.org/node/5087

> Zélus [1] is a new programming language for modeling systems that mix discrete logical time and continuous time behaviors. From a user's perspective, its main originality is to extend an existing Lustre-like synchronous language with Ordinary Differential Equations (ODEs). The extension is conservative: any synchronous program expressed as data-flow equations and hierarchical automata can be composed arbitrarily with ODEs in the same source code.

> Synchronous programming languages (à la Lucid Synchrone [2]) are language designs for reactive systems with discrete time. Zélus extends them gracefully to hybrid discrete/continuous systems, to interact with the physical world, or simulate it -- while preserving their strong semantic qualities.

[1] https://www.di.ens.fr/~pouzet/bib/hscc13.pdf

[2] https://www.di.ens.fr/~pouzet/lucid-synchrone/

Related from 2015: https://news.ycombinator.com/item?id=9350972

A similar project is Ceu[1], which is made at LabLua.

[1] - http://www.ceu-lang.org/

out of curiosity, how does reactive work with synchronicity, shouldn't it be going hand in hand with async?

My guess is that Esterel is using the word "synchronicity" for what we know as "reactive" today. Not to be confused with the "sync/async" we normally refer to blocking/non-blocking today. I could misunderstanding this though. See https://en.wikipedia.org/wiki/Synchronous_programming_langua...