Getting Clojure

Lists

Clojure has a second data type that—at least at first blush—seems a lot like the vector: the list. Like a vector, a list is an ordered collection of items. To make a list, you surround your items with round parentheses instead of the square brackets you would use for a vector:

'(1 2 3)

If you look closely at the list in that code example, you will see a second syntactic twist: the list is preceded by a single-quote character. We need that quote for a very prosaic reason: lists, with their round parentheses, look just like Clojure code. Syntactically it’s hard to tell the difference between (1 2 3) and (def x 99). The quote’s job is to stand there in front of the list and shout, Hey! The thing that comes next is data. Don’t try to execute ...