koka VS dafny

This post by the Koka-author is an update about what's currently being worked on: https://github.com/koka-lang/koka/discussions/339

Some programming language like JS, use path-based imports, that's not good for making a stabel API.

See https://api-extractor.com/pages/setup/configure_rollup/#:~:text=(The%20API%20Extractor,with%20that%20effort.)

And https://github.com/koka-lang/koka/issues/31#issuecomment-1482200826

It also offers a great Inversion of Control mechanism where everything is customisable, and, unlike Capability Objects, AESs also offer compatibility with type inference (you can pass functions doing IO to map, and it Just Works(TM)) and first-class control over stack frames (because really a continuation function is just some stack frames, which you can manually move to the heap if you want a closure; which means async is an effect!). It also is composable in ways Monads are not.

Koka and other languages implementing Algebraic Effect Systems make everything a user-defined case of coroutines: async is just another effect/Monadic type. Zig does something similar by having first class stack frames, making all function calls possibly asynchronous.

Super interesting, there is a proposal to add this to JavaScript and several languages that use this, unison, koka & eff. I had no idea this was even a thing!

Koka, already cited in this thread, early 2010s. Koka's first claim to fame was a usable effect system (at the type were, basically, effect systems were not usable in practice; in fact few languages have managed to do as well as Koka since). Now its author is working on cool implementation strategies for functional languages as well.

I'm a software engineer with 3 years of professional experience. I worked for 2 years at Microsoft on Azure Compute and now work at Google, working on improving Google search. I am the sole maintainer of the popular open-source library microlens with 80k downloads. I've also contributed to the Koka programming language developed at Microsoft Research.

By implementing all of those optimizations in the Koka programming language, they achieved GC overhead much less and execution time faster than the other languages including OCaml, Haskell, and even C++ in several algorithms and data structures that frequently keep common sub-structures of them, such as red-black trees. For more information, see the latest version of the paper.

Code correctness is a lost art. I requirement to think in abstractions is what scares a lot of devs to avoid it. The higher abstraction language (formal specs) focus on a dedicated language to describe code, whereas lower abstractions (code contracts) basically replace validation logic with a better model.

C# once had Code Contracts[1]; a simple yet powerful way to make formal specifications. The contracts was checked at compile time using the Z3 SMT solver[2]. It was unfortunately deprecated after a few years[3] and once removed from the .NET Runtime it was declared dead.

The closest thing C# now have is probably Dafny[4] while the C# dev guys still try to figure out how to implement it directly in the language[5].

[1] https://www.microsoft.com/en-us/research/project/code-contra...

[2] https://github.com/Z3Prover/z3

[3] https://github.com/microsoft/CodeContracts

[4] https://github.com/dafny-lang/dafny

[5] https://github.com/dotnet/csharplang/issues/105

I don't think something that specific exists. There are a very large number of formal methods tools, each with different specialties / domains.

For verification with proof assistants, [Software Foundations](https://softwarefoundations.cis.upenn.edu/) and [Concrete Semantics](http://concrete-semantics.org/) are both solid.

For verification via model checking, you can check out [Learn TLA+](https://learntla.com/), and the more theoretical [Specifying Systems](https://lamport.azurewebsites.net/tla/book-02-08-08.pdf).

For more theory, check out [Formal Reasoning About Programs](http://adam.chlipala.net/frap/).

And for general projects look at [F*](https://www.fstar-lang.org/) and [Dafny](https://dafny.org/).

Dafny and Whiley are two examples with explicit verification support. Idris and other dependently typed languages should all be rich enough to express the required predicate but might not necessarily be able to accept a reasonable implementation as proof. Isabelle, Lean, Coq, and other theorem provers definitely can express the capability but aren't going to churn out much in the way of executable programs; they're more useful to guide an implementation in a more practical functional language but then the proof is separated from the implementation, and you could also use tools like TLA+.

https://dafny.org/

https://whiley.org/

https://www.idris-lang.org/

https://isabelle.in.tum.de/

https://leanprover.github.io/

https://coq.inria.fr/

http://lamport.azurewebsites.net/tla/tla.html

> I think we can assume it won't be as efficient has hand written code

Actually, surprisingly, not necessarily the case!

If you'll refer to the discussion in https://github.com/dafny-lang/dafny/issues/601 and in https://github.com/dafny-lang/dafny/issues/547, Dafny can statically prove that certain compiler branches are not possible and will never be taken (such as out-of-bounds on index access, logical assumptions about whether a value is greater than or less than some other value, etc). This lets you code in the assumptions (__assume in C++ or unreachable_unchecked() under rust) that will allow the compiler to optimize the codegen using this information.

Most of the proof assistants out there: Lean, Coq, Dafny, Isabelle, F*, Idris 2, and Agda. And the main concepts are dependent types, Homotopy Type Theory AKA HoTT, and Category Theory. Warning: HoTT and Category Theory are really dense, you're going to really need to research them.

I'm not sure if the author is here, or if my comment attempt was successful. So, can I suggest you take a look at a third leg of the formal methods stool?

If you are familiar with C, check out Frama-C (https://frama-c.com/) and the WP and RTE plugins. The approach is based on Tony Hoare and EWD's axiomatic semantics (https://en.wikipedia.org/wiki/Hoare_logic). It does not have a good memory management story, as far as I know, but is very good for demonstrating value correctness (RTE automatically generates assertions for numeric runtime errors, for example) and many memory errors.

If you are familiar with Ada, check out SPARK (https://www.adacore.com/about-spark), which is similar to Frama-C but has a much better interface in the AdaCore GNAT toolkit and IDE.

Both work similarly: Assertions in normal Ada or C code as well as the code itself are translated into SMT statements and fed to a SMT solver to find counterexamples---errors.

I have some blog posts from several years ago about Frama-C:https://maniagnosis.crsr.net/tags/applied%20formal%20logic.h... (And I really should get back into it; it's a lot of fun.)

If you are not familiar with Ada or C, Dafny (https://dafny.org/) is another option based on .NET and devoleped at Microsoft. It seems nigh-on perfect for this approach. (The language uses a garbage collector.) At the time I was looking, there was little documentation on Dafny, but that seems to have improved.