6.1.2.1.1.1 Examples of for-as-arithmetic subclause

;; Print some numbers.
 (loop for i from 1 to 3
       do (print i))
>>  1
>>  2
>>  3
=>  NIL
 
;; Print every third number.
 (loop for i from 10 downto 1 by 3
       do (print i))
>>  10 
>>  7 
>>  4 
>>  1 
=>  NIL
 
;; Step incrementally from the default starting value.
 (loop for i below 3
       do (print i))
>>  0
>>  1
>>  2
=>  NIL