# Why Lean 4 replaced OCaml as my Primary Language

**URL:** <https://discuss.ocaml.org/t/why-lean-4-replaced-ocaml-as-my-primary-language/17109>\
**Category:** Ecosystem\
**Tags:** stdlib, language-design, critical, dune\
**Created:** [August 15, 2025, 5:22pm UTC](https://discuss.ocaml.org/t/why-lean-4-replaced-ocaml-as-my-primary-language/17109 "2025-08-15T17:22:14Z")\
**Posts on this page:** 1\
**Showing post:** 4

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**Author:** ![kayceesrk](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/kayceesrk/32/1936_2.png) [@kayceesrk](https://discuss.ocaml.org/u/kayceesrk)\
**Post date:** [August 16, 2025, 3:01am UTC](https://discuss.ocaml.org/t/why-lean-4-replaced-ocaml-as-my-primary-language/17109/4 "2025-08-16T03:01:57Z")

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Issue number 1 is one of the reasons Xavier Leroy cited for OCaml’s success

> [@Congratulation to the OCaml team for the 2023 SIGPLAN programming languages software award! trophy](https://discuss.ocaml.org/t/congratulation-to-the-ocaml-team-for-the-2023-sigplan-programming-languages-software-award/12437/4):
>
> It’s an honor for the whole OCaml development team to receive such a prestigious award. Some of us are here tonight: Gabriel Scherer, Damien Doligez, Florian Angeletti, Luc Maranget, David Allsopp, Stephen Dolan, Nicolas Ojeda Bär, and I’m Xavier Leroy. It’s two, almost three generations of computer scientists and developers that are being honored… There is no denying that OCaml has been a long-term project. I released the first version of OCaml, then called Objective Caml, in 1996, almost 2…

> What made that possible? Not just fancy types and nice modules – even though systems programmers value type safety and modularity highly – but also basic properties of OCaml:
> 
> - a language with a simple cost model, where it’s easy to track how much time and how much space is used;
> 
> - a compiler that produces efficient code that looks like the source code, with only predictable optimizations;
> 
> - a low-latency garbage collector, usable for soft real-time applications.

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