Re: Is there something wrong with random function?

> On 17 Nov 2017, at 21:23, Jean Louis <[email protected]> wrote:
> 
> On Fri, Nov 17, 2017 at 08:18:01PM +0100, Pascal Bourguignon wrote:
>> 
>> 
>>> On 16 Nov 2017, at 21:01, Jean Louis <[email protected]> wrote:
>>> 
>>> On Thu, Nov 16, 2017 at 06:19:56PM +0000, Don Cohen wrote:
>>>> 6 decimal digits separately you should just call
>>>> (random 1000000), and if you want leading zeros,
>>>> then format the output as "~6,'0,d".  Or if you
>>>> don't need the ones that start with zero you
>>>> could do (+ 100000 (random 900000))
>>> 
>>> (defun random-number (&key (digits 6))
>>> (setf *random-state* (make-random-state))
>>> (let ((format (format nil "~~~A,'0,d" digits)))
>>>   (format nil format
>>>           (random (read-from-string (make-string digits :initial-element #\1))))))
>>> 
>>> Something like that also works for me. Thanks for
>>> a reminder.
>> 
>> 
>> (loop for width from 2 to 6 collect (format nil "~V,'0D-~A" width (random (expt 10 width)) "base-name"))
>> ;; —> ("60-base-name" "592-base-name" "3072-base-name" "52258-base-name" "021090-base-name”)
> 
> (format nil "~V,'0D-~A" 6 (random (expt 6 6)) "base-name")
> 
> I understand however, I cannot find ~V in CLHS. Where do I find documentation for it?
> 
> I found just one reference to it in the file: Issues/iss273_w.htm


See section 22.3 Formatted Output. http://www.lispworks.com/documentation/HyperSpec/Body/22_c.htm

In place of a prefix parameter to a directive, V (or v) can be used. In this case, format <http://www.lispworks.com/documentation/HyperSpec/Body/f_format.htm#format> takes an argument from args as a parameter to the directive. The argument should be an integer <http://www.lispworks.com/documentation/HyperSpec/Body/26_glo_i.htm#integer> or character <http://www.lispworks.com/documentation/HyperSpec/Body/26_glo_c.htm#character>. If the arg used by a V parameter is nil <http://www.lispworks.com/documentation/HyperSpec/Body/a_nil.htm#nil>, the effect is as if the parameter had been omitted. # can be used in place of a prefix parameter; it represents the number of args remaining to be processed. When used within a recursive format, in the context of ~? or ~{, the # prefix parameter represents the number of format arguments <http://www.lispworks.com/documentation/HyperSpec/Body/26_glo_f.htm#format_argument> remaining within the recursive call.



-- 
__Pascal J. Bourguignon__



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