cond (ANSI and GNU Common Lisp Document)

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#### 5.3.42 cond [Macro]

`cond` {!clause}* ⇒ {result}*

clause ::=(test-form {form}*)

#### Arguments and Values::

test-form—a form.

forms—an implicit progn.

results—the values of the forms in the first clause whose test-form yields true, or the primary value of the test-form if there are no forms in that clause, or else nil if no test-form yields true.

#### Description::

cond allows the execution of forms to be dependent on test-form.

Test-forms are evaluated one at a time in the order in which they are given in the argument list until a test-form is found that evaluates to true.

If there are no forms in that clause, the primary value of the test-form is returned by the cond form. Otherwise, the forms associated with this test-form are evaluated in order, left to right, as an implicit progn, and the values returned by the last form are returned by the cond form.

Once one test-form has yielded true, no additional test-forms are evaluated. If no test-form yields true, nil is returned.

#### Examples::

     (defun select-options ()
       (cond ((= a 1) (setq a 2))
             ((= a 2) (setq a 3))
             ((and (= a 3) (floor a 2)))
             (t (floor a 3)))) ⇒  SELECT-OPTIONS
     (setq a 1) ⇒  1
     (select-options) ⇒  2
     a ⇒  2
     (select-options) ⇒  3
     a ⇒  3
     (select-options) ⇒  1
     (setq a 5) ⇒  5
     (select-options) ⇒  1, 2

#### See Also::

if , case .