[Openmcl-devel] Trunk and released version

Ron Garret ron at flownet.com
Thu Aug 13 18:13:12 UTC 2009


On Aug 13, 2009, at 10:51 AM, Tobias C. Rittweiler wrote:

> Ron Garret <ron at flownet.com> writes:
>
>> On Aug 13, 2009, at 9:12 AM, Tim Bradshaw wrote:
>>
>>> On 13 Aug 2009, at 15:55, Ron Garret wrote:
>>>
>>>> I'd call that a bug in the ANSI spec.  It violates the principle of
>>>> least surprise for no benefit whatsoever.  If X is unconditionally
>>>> bound to NIL then there is no point in even having it in scope when
>>>> the result-form is evaluated.
>>>
>>> I'm guessing it's for compatibility with DOTIMES.
>>
>> But in the case of DOTIMES the iteration variable is rebound (or
>> assigned) to a potentially useful value.  In the case of DOLIST it's
>> assigned (or rebound) to a constant (NIL) which cannot possibly serve
>> any useful purpose.
>
> It allows for an implementation based on DO*.

Huh?  How would removing the requirement of having VAR rebound (or  
reassigned) to NIL make it harder to implement DOLIST in terms of DO*?

For that matter, what would be wrong with:

(defmacro sane-dolist ((var list &optional ret) &body body)
   `(do* ((l1 ,list (cdr l1)) (,var (car l1) (car l1)))
         ((null (cdr l1)) (progn , at body) ,ret)
      , at body))

rg

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