5.3.43 if [Special Operator]

if test-form then-form [else-form] ⇒ {result}*

Arguments and Values::

Test-form—a form.

Then-form—a form.

Else-form—a form. The default is nil.

results—if the test-form yielded true, the values returned by the then-form; otherwise, the values returned by the else-form.

Description::

if allows the execution of a form to be dependent on a single test-form.

First test-form is evaluated. If the result is true, then then-form is selected; otherwise else-form is selected. Whichever form is selected is then evaluated.

Examples::

 (if t 1) ⇒  1
 (if nil 1 2) ⇒  2 
 (defun test ()
   (dolist (truth-value '(t nil 1 (a b c)))
     (if truth-value (print 'true) (print 'false))
     (prin1 truth-value))) ⇒  TEST
 (test)
 |>  TRUE T
 |>  FALSE NIL
 |>  TRUE 1
 |>  TRUE (A B C)
⇒  NIL

See Also::

cond , unless, when

Notes::

 (if test-form then-form else-form)
 ≡ (cond (test-form then-form) (t else-form))