DRY Is the Most Misunderstood Rule in Programming

This article discusses how the DRY (Don't Repeat Yourself) principle is often misinterpreted by developers. It clarifies the original definition from 'The Pragmatic Programmer,' which focuses on knowledge duplication rather than code duplication. The author warns against extracting shared code prematurely, leading to complex, hard-to-maintain abstractions with boolean flags and tangled dependencies. Using examples like address validation, it shows how identical code can represent different domain concepts, and that the cost of a wrong abstraction often exceeds the cost of duplication. The piece advocates for careful consideration before applying DRY to code.