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  ANSI Common Lisp   5 Data and Control Flow   5.3 Dictionary of Data and Control Flow

5.3.43 if Special Operator

Syntax:
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))

Allegro CL Implementation Details:
None.

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