bug#21782: 25.0.50; New functions nfront/front

[Tino Calancha <f92capac@gmail.com>]

>
> `nreverse` efficiently does what is supposed to do, yes.  But it is
> O(l), where l is the length of the list arg.
>
> In addition, the newly created `nreverse'd list must be garbage
> collected.
>
> The `copy-sequence' call in `front' is bad for the same reason.
>
> OTOH nfront can be implemented in O(n), where n is the number argument
> to nfront.

Thank you Michael for the detail answer. I appreciate it a lot.
Now i see clearly what you mean.

For all the people:
Efficiency implementations are very important, almost as important as 
have things available.
One emacs user starting one session has no available seq-take. That is
the first thing to care, efficiency comes later.

Many users learn the lenguage autocompleting in the minibuffer. If it is
not loaded the least people will realize such functions you are 
developping do exists. We develop tools to be used, not ust to be nice.

IMOP, fundamental operations should be loaded by default. If this is not 
the case, that means the function should not be located in its corrent 
location: fair and simple.

Please, consider make this fundamental operation being loaded at the 
beginning. Thanks.
I finish here because i start to repeat myself. Thank you for the very 
nice chat; it has being very instructive for me and i enjoied very much.