Re: How to avoid compiler warning `unused lexical variable' for `dolist' or `dotimes'?

[Leo Butler]

Stefan,

I wonder why the lexical-binding version of dotimes is not implemented
like:

#+begin_src emacs-lisp
  (let* ((start 0) (end (nth 1 spec)) (counter (gensym))
         (body (subst counter (car spec) body)))
          `(let ((,counter ,start))
             (while (< ,counter ,end)
               ,@body
               (setq ,counter (1+ ,counter)))
             ,@ (cddr spec))))
#+end_src

I am familiar with the comment in subr.el about uninterned symbols, but
TBH, I don't have a sense of where the performance penalty might be
of any significant size.

Leo

Jean Louis <bugs@gnu.support> writes:

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>
> * Stefan Monnier <monnier@iro.umontreal.ca> [2021-01-08 10:16]:
>> > Only it is not relevant to macro or function that is documented to
>> > work, but then again it gives warnings for `n' and not for `return' as
>> > in above example. 
>> 
>> Not sure what you mean by "documented", but `C-h f dotimes` says:
>> 
>>     dotimes is a Lisp macro in ‘subr.el’.
>>     
>>     (dotimes (VAR COUNT [RESULT]) BODY...)
>>     
>>       Probably introduced at or before Emacs version 21.1.
>>     
>>     Loop a certain number of times.
>>     Evaluate BODY with VAR bound to successive integers running from 0,
>>     inclusive, to COUNT, exclusive.
>>     
>>     Finally RESULT is evaluated to get the return value (nil if
>>     RESULT is omitted).  Using RESULT is deprecated, and may result
>>     in compilation warnings about unused variables.
>> 
>> Notice the last sentence.
>
> Now I do notice it.
>
> I do switch to `while' and mapping functions rather.
>
> Jean