Macroexpansion

• When the evaluator sees (incf a)

  • It notices that INCF names a macro
  • It “runs” or macroexpands the macro, which transforms the line of code into:
    • (setf a (+ 1 a))
  • It evaluates that expression instead
  • So when you type (incf a) to the lisp listener, it is as if you had typed (setf a (+ 1 a))

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