Don't repeat yourself (DRY) implies O(1) edits.

Authored by Mark Seemann, a software architect and consultant, this blog focuses on software design, object-oriented programming, and functional programming principles. Readers can explore articles and discussions on topics such as dependency injection, domain-driven design, and test-driven development. Additionally, they can learn about architectural patterns, design patterns, and best practices for building robust, maintainable software systems.

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Big-O notation can be applied to measure code coupling by counting the number of edits required when making changes. The DRY principle aims for O(1) edits where changes happen in one place, while duplicated code creates O(n) coupling requiring changes across multiple locations. O(1) coupling with small constants (2-3 edits) is manageable through checklists or type systems, as seen in test-specific equality or Fake objects. However, larger constants (like 6 edits in layered architectures) or true O(n) coupling (shotgun surgery, dynamic mocks) create maintenance burdens. The framework helps distinguish benign duplication with fixed edit counts from dangerous duplication that grows unbounded over time.

Coupling from a big-O perspective