(if ⟨test⟩ ⟨consequent⟩ ⟨alternate⟩) ¶(if ⟨test⟩ ⟨consequent⟩) ¶Syntax: ⟨Test⟩, ⟨consequent⟩, and ⟨alternate⟩ are expressions.
Semantics: An if expression is evaluated as follows: first,
⟨test⟩ is evaluated. If it yields a true value
(see Booleans), then ⟨consequent⟩ is evaluated and its values
are returned. Otherwise ⟨alternate⟩ is evaluated and its values
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