Programming Clojure, 2nd Edition

Notation Conventions

The following notation conventions are used throughout the book.

Literal code examples use the following font:

(+ 2 2)

The result of executing a code example is preceded by ->.

(+ 2 2)
-> 4

Where console output cannot easily be distinguished from code and results, it is preceded by a pipe character (|).

(println "hello")
| hello
-> nil

When introducing a Clojure form for the first time, we will show the grammar for the form like this:

(example-fn required-arg)
(example-fn optional-arg?)
(example-fn zero-or-more-arg*)
(example-fn one-or-more-arg+)
(example-fn & collection-of-variable-args)

The grammar is informal, using ?, *, +, and & to document different argument-passing styles, as shown previously. ...