make an element last element of a list

make an element last element of a list

[Laurent Marzullo]

Hello all,

I've got a scheme list 

SCM	scm_game_list;

and I want to add, with C API, an elements at the end of
the list.

Is there any function to do this or must I go throw the entire
list and adding a new scm_cons( new_elem , SCM_EOL ) at the end ?

Thanks
-- 
Laurent Marzullo <marzullo@la-defense.oilfield.slb.com>



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Re: make an element last element of a list

[Stephen Compall]

Laurent Marzullo <marzullo@la-defense.oilfield.slb.com> writes:

> I've got a scheme list 
> 
> SCM	scm_game_list;
> 
> and I want to add, with C API, an elements at the end of
> the list.
> 
> Is there any function to do this or must I go throw the entire
> list and adding a new scm_cons( new_elem , SCM_EOL ) at the end ?

#ifdef HUMBLE_OPINION
Maybe you don't want to hear this, but how are you building the list?
If you must have access to the list in the order in which you seem to
be working on it above *before* you add elements to the list, then you
ought to keep track of the last cell, as well as scm_game_list.

If you are building the list first, then using it, but still need the
order, then it would be best to cons new elements onto the front, then
use scm_reverse_x (saving the return value).

If you don't care about the order at all, just cons new items onto the
beginning.
#endif

--
Stephen Compall or s11 or sirian

I'm not proud.

asset Freeh TELINT ANC Baranyi MD4 Lon Horiuchi cryptanalysis PGP bomb
LLNL quiche halcon SRI colonel


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Re: make an element last element of a list

[rm]

On Tue, Oct 21, 2003 at 05:08:42PM +0200, Laurent Marzullo wrote:
> Hello all,
> 
> I've got a scheme list 
> 
> SCM	scm_game_list;
> 
> and I want to add, with C API, an elements at the end of
> the list.

If you want to destrutively modify your list you can do the
following:
 
 (define my-lst (list 1 2 3 4))
 (define new-last (list 5))
 (set-cdr! (last my-lst) new-last)

using the c functions 
 

 SCM new_last =  scm_cons( new_elem , SCM_EOL );

 scm_set_cdr_x ( scm_last_pair (my_lst),  new_last );

HTH Ralf Mattes


> Is there any function to do this or must I go throw the entire
> list and adding a new scm_cons( new_elem , SCM_EOL ) at the end ?
> 
> Thanks
> -- 
> Laurent Marzullo <marzullo@la-defense.oilfield.slb.com>
> 
> 
> 
> _______________________________________________
> Guile-devel mailing list
> Guile-devel@gnu.org
> http://mail.gnu.org/mailman/listinfo/guile-devel


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Re: make an element last element of a list

[tomas]

On Tue, Oct 21, 2003 at 05:50:09PM +0200, rm@fabula.de wrote:
> On Tue, Oct 21, 2003 at 05:08:42PM +0200, Laurent Marzullo wrote:
> > Hello all,
> > 
> > I've got a scheme list 
> > 
> > SCM	scm_game_list;
> > 
> > and I want to add, with C API, an elements at the end of
> > the list.
> 
> If you want to destrutively modify your list you can do the
> following:
>  
>  (define my-lst (list 1 2 3 4))
>  (define new-last (list 5))
>  (set-cdr! (last my-lst) new-last)

...but you don't want to do this if the lists grow too large.
Keeping track of the last cons cell resp. maintaining a
reversed list (and reversing it once at the end, if ever
necessary) as another poster suggested is more efficient.
For short lists the solution is short and sweet, though.

Don't hesitate to ask if you need examples.

Cheers
-- tomas


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Re: make an element last element of a list

[rm]

> >  (define my-lst (list 1 2 3 4))
> >  (define new-last (list 5))
> >  (set-cdr! (last my-lst) new-last)
                ^^^^
Sorry, typo, should be (last-pair ....)

 RalfD

> ...but you don't want to do this if the lists grow too large.
> Keeping track of the last cons cell resp. maintaining a
> reversed list (and reversing it once at the end, if ever
> necessary) as another poster suggested is more efficient.
> For short lists the solution is short and sweet, though.
> 
> Don't hesitate to ask if you need examples.
> 
> Cheers
> -- tomas
> 
> 
> _______________________________________________
> Guile-devel mailing list
> Guile-devel@gnu.org
> http://mail.gnu.org/mailman/listinfo/guile-devel


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