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| ANSI Common Lisp 5 Data and Control Flow 5.3 Dictionary of Data and Control Flow
5.3.42 cond | Macro
  Syntax: 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. Allegro CL Implementation Details: None.

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