Syntax: <Test>, <consequent>, and <alternate> may be arbitrary expressions.
Semantics: An ‘if’ expression is evaluated as follows: first, <test> is evaluated. If it yields a true value (see section see Booleans), then <consequent> is evaluated and its value(s) is(are) returned. Otherwise <alternate> is evaluated and its value(s) is(are) returned. If <test> yields a false value and no <alternate> is specified, then the result of the expression is unspecified.
(if (> 3 2) 'yes 'no) ==> yes (if (> 2 3) 'yes 'no) ==> no (if (> 3 2) (- 3 2) (+ 3 2)) ==> 1