The author explores the concept of invariants in programming, breaking down the term into three different categories: mathematical thinking, coding techniques, and system properties. The focus is on the importance of invariants in ensuring code correctness and system stability. The author provides examples of invariants in action, highlighting the power of explicitly defining the expected behavior of code to avoid errors. Surprisingly, the author points out a flaw in a code example and explains how thinking in invariants helped solve it. The discussion extends to large-scale programming, showcasing various system invariants in different projects. Overall, invariants simplify reasoning about complex systems, leading to better-designed code.
https://matklad.github.io/2023/10/06/what-is-an-invariant.html