# Reason

> syntax extension and toolchain for OCaml

**Wikidata**: [Q63565848](https://www.wikidata.org/wiki/Q63565848)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Reason_(programming_language))  
**Source**: https://4ort.xyz/entity/reason

## Summary
Reason is a syntax extension and toolchain for OCaml, designed to make the functional programming language more accessible and interoperable with JavaScript. It was developed by Meta (formerly Facebook) and first released in March 2016, offering a more ergonomic syntax while leveraging OCaml's robust type system and performance.

## Key Facts
- **Type**: Programming language, free and open-source software
- **Inception**: March 2016
- **Developer**: Meta (formerly Facebook)
- **License**: MIT License (since December 2017)
- **Primary Use**: Syntax extension for OCaml, targeting JavaScript interoperability
- **File Extensions**: `.re` (source files), `.rei` (interface files)
- **Latest Stable Version**: 1.13.5 (April 2017)
- **Inspired By**: OCaml
- **Paradigm**: Functional programming
- **Typing Discipline**: Static typing
- **Platform**: Cross-platform
- **Website**: [reasonml.github.io](https://reasonml.github.io/)
- **Source Code**: [GitHub repository](https://github.com/reasonml/reason)

## FAQs
### Q: What is Reason, and how does it relate to OCaml?
A: Reason is a syntax extension and toolchain for OCaml, designed to make the functional programming language more accessible. It provides a more ergonomic syntax while retaining OCaml's type system and performance, making it easier to write and maintain code.

### Q: Who developed Reason, and when was it first released?
A: Reason was developed by Meta (formerly Facebook) and was first released in March 2016. The project was later open-sourced under the MIT License in December 2017.

### Q: What are the file extensions used for Reason code?
A: Reason source files use the `.re` extension, while interface files use `.rei`.

### Q: How does Reason differ from ReScript?
A: While Reason and ReScript share some similarities, ReScript is a distinct programming language that compiles to JavaScript, whereas Reason is a syntax extension for OCaml. Both were developed by Meta but serve different purposes.

### Q: What is the latest stable version of Reason?
A: The latest stable version of Reason is 1.13.5, released in April 2017.

## Why It Matters
Reason was created to address the challenges of writing and maintaining large-scale JavaScript applications by leveraging OCaml's type system and functional programming paradigm. By providing a more ergonomic syntax for OCaml, Reason made it easier for developers to write robust, type-safe code. Its integration with JavaScript allowed for seamless interoperability, enabling developers to build high-performance applications with a more enjoyable development experience. The project's open-source nature and MIT License encouraged community contributions and adoption, further solidifying its role in the functional programming ecosystem.

## Notable For
- **Syntax Extension for OCaml**: Reason introduced a more accessible syntax for OCaml, making it easier for developers to write and maintain functional programs.
- **JavaScript Interoperability**: Reason's toolchain allowed for seamless integration with JavaScript, enabling developers to leverage OCaml's strengths in web development.
- **Open-Source Development**: Reason was open-sourced under the MIT License in December 2017, fostering community contributions and adoption.
- **Functional Programming Focus**: Reason emphasized functional programming paradigms, providing a robust type system and performance benefits.
- **Cross-Platform Compatibility**: Reason was designed to be cross-platform, ensuring broad compatibility across different operating systems.

## Body
### Overview
Reason is a syntax extension and toolchain for OCaml, developed by Meta (formerly Facebook) in March 2016. It was designed to make OCaml more accessible and interoperable with JavaScript, offering a more ergonomic syntax while retaining OCaml's type system and performance.

### Development and Release
- **Inception**: March 2016
- **Developer**: Meta (formerly Facebook)
- **License**: MIT License (since December 2017)
- **Source Code**: Hosted on [GitHub](https://github.com/reasonml/reason)

### Technical Specifications
- **File Extensions**: `.re` (source files), `.rei` (interface files)
- **Latest Stable Version**: 1.13.5 (April 2017)
- **Inspired By**: OCaml
- **Paradigm**: Functional programming
- **Typing Discipline**: Static typing
- **Platform**: Cross-platform

### Significance
Reason's primary goal was to address the challenges of writing and maintaining large-scale JavaScript applications by leveraging OCaml's type system and functional programming paradigm. Its integration with JavaScript allowed for seamless interoperability, enabling developers to build high-performance applications with a more enjoyable development experience. The project's open-source nature and MIT License encouraged community contributions and adoption, further solidifying its role in the functional programming ecosystem.

### Related Entities
- **OCaml**: The programming language that Reason extends.
- **ReScript**: A distinct programming language developed by Meta that compiles to JavaScript, though it shares some similarities with Reason.
- **Raku**: A member of the Perl family of programming languages, distinct from Reason.

## References

1. [Source](https://github.com/facebook/reason/commit/e8fb73ec6ff7c3136715a3c628769e3d5906c4f0)
2. [Release 0.0.3. 2016](https://github.com/facebook/reason/releases/tag/0.0.3)
3. [Release 0.0.3. 2016](https://github.com/reasonml/reason/releases/tag/0.0.3)
4. [Release 0.0.4. 2016](https://github.com/facebook/reason/releases/tag/0.0.4)
5. [Release 0.0.4. 2016](https://github.com/reasonml/reason/releases/tag/0.0.4)
6. [Release 0.0.5. 2016](https://github.com/facebook/reason/releases/tag/0.0.5)
7. [Release 0.0.5. 2016](https://github.com/reasonml/reason/releases/tag/0.0.5)
8. [Release 0.0.6. 2016](https://github.com/facebook/reason/releases/tag/0.0.6)
9. [Release 0.0.6. 2016](https://github.com/reasonml/reason/releases/tag/0.0.6)
10. [Release 1.11.0. 2017](https://github.com/facebook/reason/releases/tag/1.11.0)
11. [Release 1.11.0. 2017](https://github.com/reasonml/reason/releases/tag/1.11.0)
12. [npmjs](https://registry.npmjs.com/reason)
13. [Release 1.13.0. 2017](https://github.com/facebook/reason/releases/tag/1.13.0)
14. [Release 1.13.0. 2017](https://github.com/reasonml/reason/releases/tag/1.13.0)
15. [Release 1.13.2. 2017](https://github.com/facebook/reason/releases/tag/1.13.2)
16. [Release 1.13.2. 2017](https://github.com/reasonml/reason/releases/tag/1.13.2)
17. [Release 1.13.3. 2017](https://github.com/facebook/reason/releases/tag/1.13.3)
18. [Release 1.13.3. 2017](https://github.com/reasonml/reason/releases/tag/1.13.3)
19. [Release 1.13.4. 2017](https://github.com/facebook/reason/releases/tag/1.13.4)
20. [Release 1.13.4. 2017](https://github.com/reasonml/reason/releases/tag/1.13.4)
21. [Release 1.13.5. 2017](https://github.com/facebook/reason/releases/tag/1.13.5)
22. [Release 1.13.5. 2017](https://github.com/reasonml/reason/releases/tag/1.13.5)
23. [Release 1.13.6. 2017](https://github.com/facebook/reason/releases/tag/1.13.6)
24. [Release 1.13.6. 2017](https://github.com/reasonml/reason/releases/tag/1.13.6)
25. [Release 1.13.7. 2017](https://github.com/facebook/reason/releases/tag/1.13.7)
26. [Release 1.13.7. 2017](https://github.com/reasonml/reason/releases/tag/1.13.7)
27. [Release 2.0.0. 2017](https://github.com/facebook/reason/releases/tag/2.0.0)
28. [Release 2.0.0. 2017](https://github.com/reasonml/reason/releases/tag/2.0.0)
29. [Release 3.0.0. 2017](https://github.com/facebook/reason/releases/tag/3.0.0)
30. [Release 3.0.0. 2017](https://github.com/reasonml/reason/releases/tag/3.0.0)
31. [Release 3.0.3. 2017](https://github.com/facebook/reason/releases/tag/3.0.3)
32. [Release 3.0.3. 2017](https://github.com/reasonml/reason/releases/tag/3.0.3)
33. [Release 3.0.4. 2017](https://github.com/facebook/reason/releases/tag/3.0.4)
34. [Release 3.0.4. 2017](https://github.com/reasonml/reason/releases/tag/3.0.4)
35. [Release 3.0.4. 2019](https://github.com/facebook/reason/blob/master/HISTORY.md#350)
36. [Release 3.8.0. 2022](https://github.com/reasonml/reason/releases/tag/3.8.0)
37. [Release 3.8.1. 2022](https://github.com/reasonml/reason/releases/tag/3.8.1)
38. [Release 3.8.2. 2022](https://github.com/reasonml/reason/releases/tag/3.8.2)
39. [Release 3.9.0. 2023](https://github.com/reasonml/reason/releases/tag/3.9.0)
40. [Release 3.10.0. 2023](https://github.com/reasonml/reason/releases/tag/3.10.0)
41. [Release 3.11.0. 2024](https://github.com/reasonml/reason/releases/tag/3.11.0)
42. [Release 3.12.0. 2024](https://github.com/reasonml/reason/releases/tag/3.12.0)
43. [Release 3.13.0. 2024](https://github.com/reasonml/reason/releases/tag/3.13.0)
44. [Release 3.14.0. 2024](https://github.com/reasonml/reason/releases/tag/3.14.0)
45. [Release 3.15.0. 2025](https://github.com/reasonml/reason/releases/tag/3.15.0)
46. [Release 3.16.0. 2025](https://github.com/reasonml/reason/releases/tag/3.16.0)
47. [Release 3.17.0. 2025](https://github.com/reasonml/reason/releases/tag/3.17.0)
48. [Release 3.17.1. 2025](https://github.com/reasonml/reason/releases/tag/3.17.1)
49. [Release 3.17.2. 2025](https://github.com/reasonml/reason/releases/tag/3.17.2)
50. [Source](https://github.com/facebook/reason/blob/master/package.json)