[1] In this book, we use list to mean a chain of pairs terminated by the end-of-list marker. In contrast, the term list structure refers to any data structure made out of pairs, not just to lists.
[2] The value null is used in JavaScript for a variety of purposes, but in this book we shall only use it to represent the empty list.
[3] Exercise 2.20 of the original textbook deals with Scheme operators that take variable numbers of arguments. This concept exists in JavaScript, but plays a less prominent role and is therefore omitted in this adaptation. The textbook adaptors decided to sneak in currying on this occasion.
2.2.1 Representing Sequences