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Not a copy of the the value, but the value. So L1 and L2 share the same value -- the list (A B C) which was first assigned as the value of L1. L3 also has a list (A B C) as its value, but it is a different list than the one shared by L1 and L2. Even though the value of L3 looks the same as the value of L1 and L2, it is a different list because it was created by a different LIST form. So (EQ L3 L1) NIL because their values are different lists, each made of the symbols A, B, and C. Contents | Cover Chapter 2 | Chapter 3, Introduction | Chapter 3, Lesson 4 | Chapter 3, Lesson 5 | Chapter 3, Lesson 6 | Chapter 4| Copyright © 1995-2001, David B.

We'll look at special variables in Chapter 8. (setq a 987) ;; Here, A has the global value 987. (let ((a 1)) ;; Here, the binding of A to the value 1 shadows the global value. ) ;; Now the global value of A is again visible. Contents | Cover Chapter 2 | Chapter 3, Introduction | Chapter 3, Lesson 5 | Chapter 3, Lesson 6 | Chapter 3, Lesson 7 | Chapter 4| Copyright © 1995-2001, David B. Lamkins All Rights Reserved Worldwide This book may not be reproduced without the written consent of its author.

This is why you have to quote the form you want expanded. The examples in this lesson are deliberately very simple, so you can understand the basic mechanism. In general, macros are trickier to write than functions -- in Chapter 20 we'll look at the reasons and the correct techniques for dealing with more complex situations. Contents | Cover Chapter 2 | Chapter 3, Introduction | Chapter 3, Lesson 7 | Chapter 3, Lesson 8 | Chapter 3, Lesson 9 | Chapter 4| Copyright © 1995-2001, David B. Lamkins All Rights Reserved Worldwide This book may not be reproduced without the written consent of its author.