MAmatthieu_bl·Apr 14, 2026Submission
1 points · Open discussionMLanguage
mlang
Forth2021–2026
MLanguage / mlang
mlang
Compiler for the M language, used to compute the income tax of French taxpayers
11Distinct people
11Mentions
0Explicit recommenders
204GitHub stars
What to know before exploring
What it is
Compiler for the M language, used to compute the income tax of French taxpayers
GitHub
Where it is used
No documented product use has been verified yet.
What people are saying
No recommendation phrase was found in the indexed comments.
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Also in these discussions
- openfisca/openfisca-france · linked in 2 of the same discussions
Mentioned in the same Hacker News threads. That is not proof they are substitutes.
This week on Hacker News
Nov 7–Nov 14 UTC · Direct repository links and separately labeled related project stories. Indexed through 11/14/2026, 12:54:37 PM UTC.
No direct repository links were found in the indexed HN discussions over the past seven days. Older discussions are available below.
Mentions over time
HN mentions by year11 dated mentions
Observed mentions: 2021-02-15 07:13:31 UTC to 2026-04-14 07:58:57 UTC.
* An incomplete calendar period is marked with an outlined bar. Its count is not directly comparable with a full period.
Counts come from the repository’s dated source evidence. Index cutoff: 2026-11-02 08:16:59 UTC.
View mention counts and date ranges
| Period | Start (UTC) | End (exclusive, UTC) | Mentions | Submissions | Comments |
|---|---|---|---|---|---|
| 2021 | 2021-01-01 00:00:00 UTC | 2022-01-01 00:00:00 UTC | 4 | 0 | 4 |
| 2022 | 2022-01-01 00:00:00 UTC | 2023-01-01 00:00:00 UTC | 1 | 0 | 1 |
| 2023 | 2023-01-01 00:00:00 UTC | 2024-01-01 00:00:00 UTC | 3 | 0 | 3 |
| 2024 | 2024-01-01 00:00:00 UTC | 2025-01-01 00:00:00 UTC | 2 | 0 | 2 |
| 2025 | 2025-01-01 00:00:00 UTC | 2026-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2026 (partial) | 2026-01-01 00:00:00 UTC | 2027-01-01 00:00:00 UTC | 1 | 1 | 0 |
What Hacker News says
11 sourcesThe French invented their own DSL for their taxes: https://github.com/MLanguage/mlang
In A Canadian payroll dependency chartThe formulas are published in a programming language called M. There is an open source implementation [1].
> There is currently no legal guarantee of any kind about the correctness of the code produced by the Mlang compiler, or by the results produced by the interpreter of Mlang. However, authors have been in contact with DGFiP to validate Mlang, and the system passes all the private DGFiP tests as of Sept. 2022 for the version of the source files responsible for computing the tax on the 2018, 2019, 2020 and 2021 income.
[1] https://github.com/MLanguage/mlang
In A Canadian payroll dependency chartThe French have a programming language for tax related work: https://github.com/MLanguage/mlang
In CatalaLang/catala: Programming language for law specificationCatala still produces plaintext legal documents at the end of the day but can be seen as a markup language for those documents. But because that markup language is a whole lot more precise than the legal text itself, it can be a bit more versatile.
Examples of how this could be useful:
- Reducing the overhead for maintaining a list of semantic translations of that legal code into other languages. Of course the official language is the only one that is "legal" but the other translations should be close enough to effectively express the nuance provided the language outputs are maintained by people who can actually speak those languages.
- Producing machine executable proof or simulation code. This could be used for "fuzzing" the legal code to identify loopholes or unintended outcomes so that legislators can then propose improved terms to av
Read the rest
oid those issues. This is by no means "making code law" but it provides an additional tool for understanding the law and how the many different parts of the legal code interact with each other.
- Adding on to the previous example, sim code could be integrated into complex models for simulating the impact of legal changes on the economy at large or specific segments.
- Finance related code can be used to generate a tool or API for validating tax, accounting, and compliance documents (as a first pass to catch errors early and reduce overhead) as well as to even prepare some of those documents. These tools often already exist but they are one or more steps removed from the actual legal definition which increases the risk of error as well as the overhead of maintaining them (which can potentially encourage rent seeking behavior by commercial providers of these tools).
France actually is already doing this to a reasonable degree albeit the "codified" version is based on the law rather than the codified version producing plaintext law. The DGFiP [1] maintains a gitlab organisation [2] that includes both Catala and MLang [3] representations of different parts of the french legal code for exactly these purposes.
1. https://fr.wikipedia.org/wiki/Direction_g%C3%A9n%C3%A9rale_d...
2. https://gitlab.adullact.net/dgfip
3. https://github.com/MLanguage/mlang
french tax code has a semi-official DSL syntax
https://github.com/MLanguage/mlang
just adopt theirs, add a message layer, and call it done
In IRS builds task force to explore running its own free e-file systemFrance has an open source implementation of their tax code [0]. The paper [1] gives an overview of the implementation language, mlang.
[0] https://github.com/MLanguage/mlang
[1] https://arxiv.org/abs/2011.07966
In Show HN: Calculator for US individual income tax, from 1970-presentThe french initiative started in 2013 is still alive (last commit a few days ago), and passes the gov test suite (they keep in touch with our version of the IRS): https://github.com/openfisca/openfisca-france
The way we got this is interestingly twisted.
French citizens requested the software used by the administration, and they managed to get it!
But, it was written in Mlang, a proprietary language created by the french administration in the 90: https://github.com/MLanguage/mlang.
Someone then decided to create an OCaml compiler that takes mlang and emits python: https://arxiv.org/abs/2011.07966
As a result, we got Open Fisca. I now think there are other techs in the mix...
A slide of the story: https://www.slideshare.net/Etalab/opening-up-the-french-tax-...
But I believe it should be mandatory for the state to provide the source of ever
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y softwares they use internally to manage our lives. Also a test suite to allow any citizen to validate their own effort to comply with the law.
Just like laws should be published as diff of the previous laws, in a VCS repo.
There have been attempts by the French and Dutch governments to codify parts of tax law as a trial of sorts, check out M for one https://github.com/MLanguage/mlang
Nevertheless, such efforts cover minimal portions already very clearly defined and debated. As another commenter replied, reforms are rarely undertaken for various reasons. One great issue with tax law is also that whatever code you may write is not necessarily guaranteed to be 'better' (fairness, revenue collected, lack of loopholes and edge cases, completeness, correctness... pick your metric) simply because it's code. That's what I thought too; but no longer.
In Legalese – Computational Law--> https://github.com/MLanguage/mlang
"Compiler for the M language, used to compute the income tax of French taxpayers"
In Templating for LawyersYou might be interested in the French example, if you don’t know already. They designed the Mlang DSL for tax calculation, and released a bunch of things on GitHub.
Here is the compiler:
https://hal.inria.fr/hal-03002266v3/document
https://github.com/MLanguage/mlang
They’ve also open sourced an official calculator, along with web APIs:
https://github.com/openfisca/openfisca-france
In Show HN: ustaxes.org – open-source tax filing webapp