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- Common Lisp macros are used to implement a minimalist Forth interpreter, demonstrating macro power and flexibility.
- Forth's key concepts—abstract registers, threaded code, immediacy (compile-time execution), and dictionary—are implemented using Lisp data structures and metaprogramming.
- The chapter emphasizes 'duality of syntax': the ability to change program semantics with minimal code modifications, a core advantage of macros.
- Forth's threaded code allows transparent control over compilation, enabling features like tail calls, recursion, and custom control structures (if/then, begin/again).
- The final code converts Forth threads into executable Lisp code (flubifying), showing cross-language translation via macros.
- Macros let Lisp overcome 'Flub' language limitations (opaque code blocks), enabling non-local branches and stack manipulation.