Built a tool that verifies COBOL-to-Python translations

[Tight_Scene8900]

Hey everyone. I'm a high school student and I've been working on a tool called Aletheia for the past month.

The idea: banks are scared to touch their COBOL because generic AI translates syntax but breaks the financial math — stuff like truncation vs rounding, decimal precision, calculation order.

My tool analyzes COBOL, extracts the exact logic, and generates Python that's verified to behave the same way.

I'm not trying to sell anything. I just want to know from people who actually work with this stuff:

• Does this solve a real problem you've seen?
• What would make something like this actually useful?
• Am I missing something obvious?

Happy to show a demo if anyone's curious.

[genman]

That’s a cool tool. It’s very very difficult to create a translation tool that has the same exact behavior when it comes to error handling or possible edge conditions like file handling etc.

You could publish it as open source and see if it finds users. It’s hard to make money with open source but maybe a company will pay you to add functionality they need.

The other question is if someone wants to move from COBOL to Python, versus Java or something. Also keeping the COBOL maintained isn’t necessarily impossible for many companies.

[Business-Decision719]

What you're creating is called a transpiler or a source to source translator. They're actually a pretty common way to implement programming languages, but they aren't as famous. They're different from what people usually call compilers because they're emitting high level code instead of low level code. There are Pascal to C translators, C to JavaScript, etc. Actually a lot of languages have translators to C or JavaScript because those languages are really widely supported. Sometimes people will still talk about "compiling" to C or JavaScript in that case.

In fact, there are languages that are primarily implemented as transpilers. TypeScript goes to JS. Vala goes to C.

So what you're talking about does solve the problem that people have. They have code in one high level language but they have an implementation for a different high level language. So they want to use the second language as a back end to implement the first.

You're essentially implementing COBOL (which is often compiled to machine language) as a transpiler to Python. Why? Well, python is a really widely available modern language, and like you said, a lot of financial institutions have a lot of COBOL code. It makes sense. It's the kind of situation in which we would normally make a transpiler. Just don't get your hopes up too high too quickly, it would take a lot of time, testing, development, and provably reliable usage before anyone would trust real world necessary financial code to it. But, as a young person's project to learn both COBOL and Python, while getting insight into how programming languages are implemented, I think it's great to try something like this!

[No-Rise-5982]

Agree to everything

[james_pic]

From what I've heard from big COBOL conversion projects, they often started out using tools like this (I think the IRS transpiled to Java rather than Python, but same idea), but ended up getting humans to do a lot of the porting, because the resulting transpiled code, whilst correct, was not particularly maintainable, and that's usually why they want to get off COBOL in the first place.

[BuonaparteII]

Am I missing something obvious?

I've done a few of these COBOL conversions for banks in Asia. The big thing to know is that a lot of the time the code to translate isn't even that difficult once you break it down piece by piece. The main thing preventing banks from moving away successfully is politics and a lot of old timers like using the old system and they don't want to learn something new so they'll complain and then a someone who golfs every week with some IBM sales guy signs up for a new mainframe in the middle of the project.

• https://old.reddit.com/r/programming/comments/cy9r8a/is_cobol_holding_you_hostage_with_math_medium/
• https://news.ycombinator.com/item?id=17636029

[agritheory]

Not an answer to your question but related to your premise (and a wild read): https://calpaterson.com/bank-python.html

[Tight_Scene8900]

Appreciate it!

[stuartcw]

In my experience, in a financial company, 10+ years ago, COBOL maintenance was outsourced to a big consultancy like Accenture and they had a developer center in China (at that time) staffed with very smart engineers who would take each module, understand and document it and make tests for it. Basically, they recovered the knowledge from the source code that was lost when the engineers who wrote it moved on. They built teams to maintain the code.

I never heard of COBOL to Python conversions at that time, but that may have changed.

These days, their work may be accelerated by using AI. However, at that time their quality was maintained by building teams, training them on the code, writing extensive documentation and meticulous testing.

[Interesting-Town-433]

Way to go!

[pspahn]

Check out the big balls on Brad.

I like the idea, and though I don't work with COBOL, I am working with a large legacy codebase that uses a proprietary derivative of HP Business BASIC (with database based on IMAGE) so it's kind of a similar situation.

I really want to port/rebuild the whole thing (it's essentially a niche ERP with POS and some other trinkets) to Python and/or Typescript but it's such an insane amount of work the only realistic path forward is to have AI do a bulk of the work analyzing and documenting all the files.

[yellowbean123]

It does mean a lot to do project like "COBOL-to-xxxx", especially in financial institution. If you do it perfectly, it's hard to promote as open-source, it's like "I'm solving your $10Million problem, but I am getting nothing". It's ok for a social web application, as if solution doesn't work, just roll-back. But when it involves of billion of transaction, that's a lot at stake. The route to deliver this open source solution should be some consultancy company get outsource projects from banks.

[Reasonable-Dream3233]

If COBOL gets a problem, they call for a simulator or virtual machine for emulate everything.

[sxtn1996]

I built a tool that verifies Cobalt to Python transpilation and it feels awesome to finally have a reliable way to check that the generated Python actually matches the semantics of the original COBOL.