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

5.3.44 or Macro

or {form}*    {results}*

Arguments and Values:
form - a form.

results - the values or primary value (see below) resulting from the evaluation of the last form executed or nil.

or evaluates each form, one at a time, from left to right. The evaluation of all forms terminates when a form evaluates to true (i.e., something other than nil).

If the evaluation of any form other than the last returns a primary value that is true, or immediately returns that value (but no additional values) without evaluating the remaining forms. If every form but the last returns false as its primary value, or returns all values returned by the last form. If no forms are supplied, or returns nil.

 (or)   NIL 
 (setq temp0 nil temp1 10 temp2 20 temp3 30)  30
 (or temp0 temp1 (setq temp2 37))  10
 temp2  20
 (or (incf temp1) (incf temp2) (incf temp3))  11
 temp1  11
 temp2  20
 temp3  30
 (or (values) temp1)  11
 (or (values temp1 temp2) temp3)  11
 (or temp0 (values temp1 temp2))  11, 20
 (or (values temp0 temp1) (values temp2 temp3))  20, 30

See Also:
and, some, unless

Allegro CL Implementation Details:

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