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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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