[kazinator]

> It's about math and software engineering.

Good idea; can you explain it in terms of software engineering? What software engineering problem is it solved by this lemma?

E.g. Starting with this set of requirements, we are transported to a solution thusly: ...

[gergoerdi]

Here's an example where I used, if not the Yoneda lemma, its categorical dual the co-Yoneda lemma (named `MarketRequest` in this post because I didn't know about it at that point so had to reinvent it to my particular use case) to solve a very real software engineering problem: http://unsafePerform.IO/blog/2012-12-01-static_analysis_with...

[gclaramunt]

Category theory is about abstraction and composition, fundamental tools in software engineering...