1.3.3 Evaluation Notation

A Lisp expression that you can evaluate is called a form. Evaluating a form always produces a result, which is a Lisp object. In the examples in this manual, this is indicated with ‘’:

(car '(1 2))
     ⇒ 1

You can read this as “(car '(1 2)) evaluates to 1”.

When a form is a macro call, it expands into a new form for Lisp to evaluate. We show the result of the expansion with ‘’. We may or may not show the result of the evaluation of the expanded form.

(third '(a b c))
     → (car (cdr (cdr '(a b c))))
     ⇒ c

To help describe one form, we sometimes show another form that produces identical results. The exact equivalence of two forms is indicated with ‘’.

(make-sparse-keymap) ≡ (list 'keymap)