cond {!clause}* ⇒ {result}*
| clause | ::= | (test-form {form}*) |
| 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. |
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.
(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
if, ‘case; ccase; ecase’ .