DRY
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External
- Pragmatic Programmer, The: From Journeyman to Master by Andrew Hunt and David Thomas
Internal
Overview
Don't Repeat Yourself (DRY) principle sys: "Every piece of knowledge should have a single, unambiguous, authoritative representation within a system."
If you are in the position to write the second time the same behavior (copy-and-paste) that means the behavior belongs into a reusable function. Duplication forces people to make a change in multiple places, and that is not good.
DRY and Coupling
Duplication Considered Useful
The DRY principle discourages duplicating the implementation of a concept, which is not the same as duplicating literal lines of code. Having multiple components depend on shared code can create tight coupling, making it hard to change.
Organizatorium
- The "rule of three" for software reuse suggests the you should turn something into a reusable component when you find three places that you need to use it. https://blog.codinghorror.com/the-delusion-of-reuse/ Facts and Fallacies of Software Engineering https://www.amazon.com/exec/obidos/ASIN/0321117425/