The Conditionals: if and Beyond
Now that you understand how Lisp handles true and false, let’s look at
if and some of the other conditional commands.
One Thing at a Time with if
if command can be used to make different things happen when things are true (such as when 1 + 2 = 3) or false (such as when 1 + 2 = 4).
(if (= (+ 1 2) 3)
(if (= (+ 1 2) 4)
if command can also be used to check whether a list is empty:
So far, the only way to branch on a condition that we’ve looked at has been the
(if (oddp 5)