About elisp, Lossing data after sort

About elisp, Lossing data after sort

[htbest2000]

Hi,

I am using "GNU Emacs 22.0.94.1 (i386-mingw-nt5.0.2195) of
2007-02-24 on NEUTRINO"

I'm writting a function to generate a series of random numbers,
it seems work fine alone. But the data always lost after sort,
following is the code:


(defun random-list (n)
  "return a list with random numbers from [0,N), length of N"
  (let ((i 0) (list nil))
    (while (< i n)
      (progn (setq list (cons (random n) list))
	     (setq i (+ 1 i))))
    list))

(defun main (n)
  "program entry"
  (let ((list nil))
    (setq list (random-list n))
    (princ (format "%S\n" list))  ;print list
    (sort list '<)
    (princ (format "%S\n" list))  ;print same again
    nil
    ))


For example, running:  (main 10)

the result:
(9 2 8 4 7 8 1 1 9 3)
(9 9)

 What's wrong in my code? Thanks

Re: About elisp, Lossing data after sort

[Barry Margolin]

In article <1173837100.827152.92620@l75g2000hse.googlegroups.com>,
 "htbest2000" <htbest2000@gmail.com> wrote:

> Hi,
> 
> I am using "GNU Emacs 22.0.94.1 (i386-mingw-nt5.0.2195) of
> 2007-02-24 on NEUTRINO"
> 
> I'm writting a function to generate a series of random numbers,
> it seems work fine alone. But the data always lost after sort,
> following is the code:
> 
> 
> (defun random-list (n)
>   "return a list with random numbers from [0,N), length of N"
>   (let ((i 0) (list nil))
>     (while (< i n)
>       (progn (setq list (cons (random n) list))
> 	     (setq i (+ 1 i))))
>     list))
> 
> (defun main (n)
>   "program entry"
>   (let ((list nil))
>     (setq list (random-list n))
>     (princ (format "%S\n" list))  ;print list
>     (sort list '<)

Change that to:

      (setq list (sort list '<))

>     (princ (format "%S\n" list))  ;print same again
>     nil
>     ))
> 
> 
> For example, running:  (main 10)
> 
> the result:
> (9 2 8 4 7 8 1 1 9 3)
> (9 9)
> 
>  What's wrong in my code? Thanks

-- 
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***
*** PLEASE don't copy me on replies, I'll read them in the group ***

Re: About elisp, Lossing data after sort

[htbest2000]

On Mar 14, 12:39 pm, Barry Margolin <bar...@alum.mit.edu> wrote:
> In article <1173837100.827152.92...@l75g2000hse.googlegroups.com>,
>
>
>
>  "htbest2000" <htbest2...@gmail.com> wrote:
> > Hi,
>
> > I am using "GNU Emacs 22.0.94.1 (i386-mingw-nt5.0.2195) of
> > 2007-02-24 on NEUTRINO"
>
> > I'm writting a function to generate a series of random numbers,
> > it seems work fine alone. But the data always lost after sort,
> > following is the code:
>
> > (defun random-list (n)
> >   "return a list with random numbers from [0,N), length of N"
> >   (let ((i 0) (list nil))
> >     (while (< i n)
> >       (progn (setq list (cons (random n) list))
> >         (setq i (+ 1 i))))
> >     list))
>
> > (defun main (n)
> >   "program entry"
> >   (let ((list nil))
> >     (setq list (random-list n))
> >     (princ (format "%S\n" list))  ;print list
> >     (sort list '<)
>
> Change that to:
>
>       (setq list (sort list '<))
>
> >     (princ (format "%S\n" list))  ;print same again
> >     nil
> >     ))
>
> > For example, running:  (main 10)
>
> > the result:
> > (9 2 8 4 7 8 1 1 9 3)
> > (9 9)
>
> >  What's wrong in my code? Thanks
>
> --
> Barry Margolin, bar...@alum.mit.edu
> Arlington, MA
> *** PLEASE post questions in newsgroups, not directly to me ***
> *** PLEASE don't copy me on replies, I'll read them in the group ***

Thanks in advance!

Re: About elisp, Lossing data after sort

[htbest2000]

On Mar 14, 12:39 pm, Barry Margolin <bar...@alum.mit.edu> wrote:
> In article <1173837100.827152.92...@l75g2000hse.googlegroups.com>,
>
>
>
>  "htbest2000" <htbest2...@gmail.com> wrote:
> > Hi,
>
> > I am using "GNU Emacs 22.0.94.1 (i386-mingw-nt5.0.2195) of
> > 2007-02-24 on NEUTRINO"
>
> > I'm writting a function to generate a series of random numbers,
> > it seems work fine alone. But the data always lost after sort,
> > following is the code:
>
> > (defun random-list (n)
> >   "return a list with random numbers from [0,N), length of N"
> >   (let ((i 0) (list nil))
> >     (while (< i n)
> >       (progn (setq list (cons (random n) list))
> >         (setq i (+ 1 i))))
> >     list))
>
> > (defun main (n)
> >   "program entry"
> >   (let ((list nil))
> >     (setq list (random-list n))
> >     (princ (format "%S\n" list))  ;print list
> >     (sort list '<)
>
> Change that to:
>
>       (setq list (sort list '<))
>
> >     (princ (format "%S\n" list))  ;print same again
> >     nil
> >     ))
>
> > For example, running:  (main 10)
>
> > the result:
> > (9 2 8 4 7 8 1 1 9 3)
> > (9 9)
>
> >  What's wrong in my code? Thanks
>
> --
> Barry Margolin, bar...@alum.mit.edu
> Arlington, MA
> *** PLEASE post questions in newsgroups, not directly to me ***
> *** PLEASE don't copy me on replies, I'll read them in the group ***

Thanks in advance!

Re: About elisp, Lossing data after sort

[htbest2000]

On Mar 14, 12:39 pm, Barry Margolin <bar...@alum.mit.edu> wrote:
> In article <1173837100.827152.92...@l75g2000hse.googlegroups.com>,
>
>
>
>  "htbest2000" <htbest2...@gmail.com> wrote:
> > Hi,
>
> > I am using "GNU Emacs 22.0.94.1 (i386-mingw-nt5.0.2195) of
> > 2007-02-24 on NEUTRINO"
>
> > I'm writting a function to generate a series of random numbers,
> > it seems work fine alone. But the data always lost after sort,
> > following is the code:
>
> > (defun random-list (n)
> >   "return a list with random numbers from [0,N), length of N"
> >   (let ((i 0) (list nil))
> >     (while (< i n)
> >       (progn (setq list (cons (random n) list))
> >         (setq i (+ 1 i))))
> >     list))
>
> > (defun main (n)
> >   "program entry"
> >   (let ((list nil))
> >     (setq list (random-list n))
> >     (princ (format "%S\n" list))  ;print list
> >     (sort list '<)
>
> Change that to:
>
>       (setq list (sort list '<))
>
> >     (princ (format "%S\n" list))  ;print same again
> >     nil
> >     ))
>
> > For example, running:  (main 10)
>
> > the result:
> > (9 2 8 4 7 8 1 1 9 3)
> > (9 9)
>
> >  What's wrong in my code? Thanks
>
> --
> Barry Margolin, bar...@alum.mit.edu
> Arlington, MA
> *** PLEASE post questions in newsgroups, not directly to me ***
> *** PLEASE don't copy me on replies, I'll read them in the group ***

Thanks in advance!

Re: About elisp, Lossing data after sort

[Pascal Bourguignon]

"htbest2000" <htbest2000@gmail.com> writes:
> On Mar 14, 12:39 pm, Barry Margolin <bar...@alum.mit.edu> wrote:
>> In article <1173837100.827152.92...@l75g2000hse.googlegroups.com>,
>>  "htbest2000" <htbest2...@gmail.com> wrote:
>> >     (sort list '<)
>>
>> Change that to:
>>
>>       (setq list (sort list '<))
>>
> Thanks in advance!

Too late!


But do you understand why you should use (setq list (sort list '<))
instead of merely (sort list '<)?

-- 
__Pascal Bourguignon__
http://www.informatimago.com
http://pjb.ogamita.org

Re: About elisp, Lossing data after sort

[htbest2000]

On Mar 14, 4:48 pm, Pascal Bourguignon <p...@informatimago.com> wrote:
> "htbest2000" <htbest2...@gmail.com> writes:
> > On Mar 14, 12:39 pm, Barry Margolin <bar...@alum.mit.edu> wrote:
> >> In article <1173837100.827152.92...@l75g2000hse.googlegroups.com>,
> >>  "htbest2000" <htbest2...@gmail.com> wrote:
> >> >     (sort list '<)
>
> >> Change that to:
>
> >>       (setq list (sort list '<))
>
> > Thanks in advance!
>
> Too late!
>
> But do you understand why you should use (setq list (sort list '<))
> instead of merely (sort list '<)?
>
> --
> __Pascal Bourguignon__http://www.informatimago.comhttp://pjb.ogamita.org

I'm sorry for my post repeatly. I am using google to post on
internet-bar( low speed ), not tin likes clients.

There something wrong in function `random-list', right? I think
the key is: (setq list (cons (random n) list)). But I don't know
why.

Would you(or others) give an reasonable explanation? Thanks

Re: About elisp, Lossing data after sort

[Joost Kremers]

htbest2000 wrote:
[sort loses data]
> There something wrong in function `random-list', right? I think
> the key is: (setq list (cons (random n) list)). But I don't know
> why.

no, the problem is with the function sort. this is a destructive function,
which means that the data structure that is passed to it as an argument
gets modified. you therefore need to catch the return value of sort and
store it. see the documentation for sort in the elisp manual.

-- 
Joost Kremers                                      joostkremers@yahoo.com
Selbst in die Unterwelt dringt durch Spalten Licht
EN:SiS(9)