---
title: "Simple math with regular expressions?"
url: "https://osherove.com/blog/2004/11/8/simple-math-with-regular-expressions.md"
canonical: "https://osherove.com/blog/2004/11/8/simple-math-with-regular-expressions.html"
published: "2004-11-08T18:00:00"
updated: "2004-11-08T18:00:00"
tags: [".Net Original"]
author: "Roy Osherove"
description: "A friend of mine (Ariel) made the bold claim that it is possible to write a regular expression (in today's languages such as .Net) that checks simple mathematical functions, for example if a number is divisible by 3. I…"
usage: "Licensed under CC BY 4.0 — reuse, quote and adapt with attribution (Roy Osherove, link to the original page)."
license: "https://creativecommons.org/licenses/by/4.0/"
---

# Simple math with regular expressions?

By Roy Osherove November 8, 2004 In [.Net Original](https://osherove.com/blog/category/net-original)

**Historical article** · Originally published November 8, 2004; technical details may be outdated.

A friend of mine (Ariel) made the bold claim that it is possible to write a regular expression (in today's languages such as .Net) that checks simple mathematical functions, for example if a number is divisible by 3. I looked and looked and asked and checked and could find no mention of this. I'm not talking theoretically; I'm looking for an example that shows me this. Can you provide one?

## More in .Net Original

[All posts in .Net Original](https://osherove.com/blog/category/net-original)

- Nov 19, 2004

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- Nov 17, 2004

    ### [Israeli .Net Deep Dive chat going on right now](https://osherove.com/blog/2004/11/17/israeli-net-deep-dive-chat-going-on-right-now.html)

- Oct 19, 2004

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- Oct 15, 2004

    ### [Solving Team Development with web projects hell](https://osherove.com/blog/2004/10/15/solving-team-development-with-web-projects-hell.html)


---

## About the author

**Roy Osherove**: Senior Solutions Architect at AWS working on AI for production and AI-driven development; author of The Art of Unit Testing and Elastic Leadership, with about 20 years of consulting and training on unit testing, TDD, team leadership and continuous delivery.

### Sites

- [RobotPaper](https://robotpaper.ai/): This blog: AI patterns and anti-patterns, AI and coding agents, and engineering leadership.
- [osherove.com](https://osherove.com): Roy's personal site. Author of The Art of Unit Testing and Elastic Leadership; consulting and training on unit testing, TDD, team leadership and continuous delivery, plus about 20 years of blog posts.
- [The Art of Unit Testing](https://www.artofunittesting.com): The Art of Unit Testing, 3rd Edition (Manning): readable, maintainable, trustworthy unit tests, plus TDD workshops in C#, JavaScript, Java and Kotlin.
- [5whys.com](https://www.5whys.com): Roy's writing on software team leadership: self-organizing teams, surviving chaos, learning mode and the Elastic Leadership model.
- [Pipeline Driven](https://pipelinedriven.org): Continuous delivery and DevOps practices: build patterns, pipeline-friendly testing, DevOps metrics and enterprise DevOps.
- [Elastic Leadership](https://www.elasticleadership.com): Elastic Leadership, Roy's framework for software team leaders (survival, learning and self-organizing modes).

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### License

Licensed under CC BY 4.0 — reuse, quote and adapt with attribution (Roy Osherove, link to the original page). License: https://creativecommons.org/licenses/by/4.0/