From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: arthur miller Newsgroups: gmane.emacs.devel Subject: Sv: Is this a bug in while-let or do I missunderstand it? 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List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Original-Sender: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Xref: news.gmane.io gmane.emacs.devel:325337 Archived-At: --_000_DU2PR02MB10109C688CA799A95D028E4A1965E2DU2PR02MB10109eu_ Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable >But if it did it that way, the condition (init-form) would only be >evaluated once, and I=92d find *that* counterintuitive. Consider the ? I don't know man. Why would it be so? Loops conditions should always be evaluated in a loop, otherwise how should loop terminate? But I don't expect a loop to re-initiate all bindings from defaults each time it runs an iteration. It is both expensive, unnecessary and counterintuitive. Don't you think? >usual form of a while loop: > > (while-let ((run (some-condition))) > (message "running")) > >Do you expect that to evaluate (some-condition) once, then, if it=92s >initially true, run forever? That usual form of while loop works because (some-condition) is a function, and it obviously computes its condition based on the external environment. Perhaps you can set some global value in the loop to stop the evaluation, o= r perhaps (some-condition) computes the terminating condition based on some other volatile values from the environment. I don't see is that in the conflict to what I say. If you instead write (while-let ((run some-condition)) (message "running")) Than yes, the loop will not terminate unless you terminate it from the loop= . However, since we are throwing away the bindings on each iteration, we are also throwing away the previously computed binding, we can't write: (while-let ((run some-condition)) (message "running") (setf run nil)) Which to me seems counterintuitive. ________________________________ Fr=E5n: Yuri Khan Skickat: den 9 november 2024 15:04 Till: arthur miller Kopia: emacs-devel@gnu.org =C4mne: Re: Is this a bug in while-let or do I missunderstand it? On Sat, 9 Nov 2024 at 20:47, arthur miller wrote: > If it wasn't clear, the unintuitive part is that while-let was to > establish the local environment, so that we don't need to type: > > (let ((som-var (init-form))) > (while some-var > ... )) But if it did it that way, the condition (init-form) would only be evaluated once, and I=92d find *that* counterintuitive. Consider the usual form of a while loop: (while-let ((run (some-condition))) (message "running")) Do you expect that to evaluate (some-condition) once, then, if it=92s initially true, run forever? --_000_DU2PR02MB10109C688CA799A95D028E4A1965E2DU2PR02MB10109eu_ Content-Type: text/html; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable
>But if it did it that way, the condition (init-form) would only be
>evaluated once, and I=92d find *that* counterintuitive. Consider the

?

I don't know man. Why would it be so? Loops conditions should always be
evaluated in a loop, otherwise how should loop terminate? But I don't
expect a loop to re-initiate all bindings from defaults each time it
runs an iteration. It is both expensive, unnecessary and counterintuitive.<= /div>
Don't you think?

>usual form of a while loop:
>
>    (while-let ((run (some-condition)))
>      (message "running"))
>
>Do you expect that to evaluate (some-condition) once, then, if it=92s
>initially true, run forever?

That usual form of while loop works because (some-condition) is a function,=
and it obviously computes its condition based on the external environment.<= /div>

Perhaps you can set some global value in the loop to stop the evaluation, o= r
perhaps (some-condition) computes the terminating condition based on some
other volatile values from the environment. I don't see is that in the
conflict to what I say.

If you instead write

(while-let ((run some-condition))
   (message "running"))

Than yes, the loop will not terminate unless you terminate it from the loop= .
However, since we are throwing away the bindings on each iteration, we are<= /div>
also throwing away the previously computed binding, we can't write:

(while-let ((run some-condition))
   (message "running")
   (setf run nil))

Which to me seems counterintuitive.
Fr=E5n: Yuri Khan <yuri.= v.khan@gmail.com>
Skickat: den 9 november 2024 15:04
Till: arthur miller <arthur.miller@live.com>
Kopia: emacs-devel@gnu.org <emacs-devel@gnu.org>
=C4mne: Re: Is this a bug in while-let or do I missunderstand it?
 
On Sat, 9 Nov 2024 at 20:47, arthur miller <art= hur.miller@live.com> wrote:

> If it wasn't clear, the unintuitive part is that while-let was to
> establish the local environment, so that we don't need to type:
>
> (let ((som-var (init-form)))
>     (while some-var
>         ... ))

But if it did it that way, the condition (init-form) would only be
evaluated once, and I=92d find *that* counterintuitive. Consider the
usual form of a while loop:

    (while-let ((run (some-condition)))
      (message "running"))

Do you expect that to evaluate (some-condition) once, then, if it=92s
initially true, run forever?
--_000_DU2PR02MB10109C688CA799A95D028E4A1965E2DU2PR02MB10109eu_--