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Clean Code 60 XP · 6 min

Duplication & Abstraction

Recognize hidden duplication and choose the right abstraction to eliminate it.

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Duplication Is Always a Design Flaw

Every piece of duplication is a missed abstraction. The question is not "should I remove this duplicate?" — the answer is always yes. The question is "what is the right abstraction?"

Types of Duplication

Obvious: identical code blocks. Subtle: same algorithm in different forms. Structural: same data shape defined multiple times. Switch/if-else: the same condition scattered across the codebase.

Code Challenge

Find the duplication type, then choose the right abstraction.

Key takeaway

Name the thing you're duplicating. The right abstraction reveals itself once you can articulate the concept.

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