cogent VS py4j

Cogent, late 2010s, a language with linear types for verification. The idea is that you write functional-looking code that is easy to verify using the functional semantics, but with an efficient compilation strategy enabled by linear types to get realistic system programs.

Of course. Here was the first incarnation: https://github.com/amw-zero/sligh. It has a decent overview of the idea in the readme. To sum it up here, the idea is: have a language built around model-driven development and model-based testing, where you write a simple model of an application, and the implementation and model-based tests are compiled for you. I wrote about the overall model-based testing strategy here. This idea comes from self-certifying compilers that produce proofs of their correctness such as Cogent, but we drop the formality requirement and use property-based testing to compare the implementation and model.

That made me think of this project Cogent. This is almost certainly not what you’re looking for, because it’s aimed at formal verification. But, it does have some interesting properties, like manual memory management through uniqueness types. It doesn’t even support recursion though so, probably not so good as a general purpose PL.

https://github.com/NICTA/cogent is for auto generating isabelle theorems + C code.