Macros are one of Clojure’s superpowers—and one of its easiest footguns. This chapter teaches what macros actually are (code that writes code), how to reason about expansion, and how to decide when a macro is justified.
For Java developers, a good analogy is “compile-time transformation,” but with much more direct access to syntax. The important discipline is to keep macros small, predictable, and boring: most problems are still better solved with functions and data.
If you take one habit away, let it be this: reach for macroexpand early and often, and always read the expanded code as if you were reviewing it in a pull request.
In this section
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Macros
What macros are, what they expand to, and how to read them safely.
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Writing Basic Macros
How to generate code with syntax-quote, unquote, and gensyms—without surprises.
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Understanding Macro Expansion
Use macroexpand to debug macros by inspecting the code they generate.
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When to Use Macros
A decision framework: use macros for syntax and evaluation control, not for cleverness.
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Advanced Macro Techniques
Patterns for code generation once you’ve mastered expansion, hygiene, and readability.
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Metaprogramming Concepts
The core ideas behind macros: code as data, quoting, and evaluation.
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Macros vs Java Reflection
Macros expand code at compile time; reflection discovers types/members at runtime.
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Common Pitfalls with Macros
Avoid multiple evaluation, variable capture, and unreadable expansions.
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Practical Macro Examples
Recognize the macro patterns you’ll see in real code and learn how to read them.
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Creating Useful Macros: Exercises for Clojure Developers
Explore practical exercises to master macro creation in Clojure, enhancing your functional programming skills and understanding of metaprogramming.