RE: [patch] minor patch for register.el

[Drew Adams]

> ( I'm cheering those who are working on improving register:)
>   I used to try but I could not show a good result[1][2].
>   I still believe register facility should be imporved 
>   massively. )
>
> [1] 
> https://lists.gnu.org/archive/html/emacs-devel/2004-03/msg00345.html
> [2] 
> https://lists.gnu.org/archive/html/emacs-devel/2004-03/msg00349.html

I don't disagree that registers could be more useful.  Dunno about "massively",
but I'm sure some more could be done.  (More could also be done with Lisp
variables for interactive use, IMO.)

Something I use are some trivial commands that copy register contents to a
variable and vice versa.  Likewise, copy between a register and the last kill.
Nothing spectacular.  (I took the `register-*able-p' functions for the patch
from that code, BTW.)

> > 4. In `list-registers': Raise error if `register-alist' is empty.
> 
> Just question.  Is this error raising really needed?

Personally, I don't really care one way or the other - (a) show a message and do
nothing or (b) raise an error.

IMO, a message (error or not) is more useful in this case than opening an empty
`*Output*' buffer showing there are no registers.  In my case, FWIW, that pops
up a new frame - silly, if not quite annoying.

(I probably should also have proposed a new name for that buffer, BTW -
`*Output*' suggests that little reflection went into the name.  `*Registers*' or
`*Register List*' would be better.)

Now, there could be a question whether `list-registers' also has some
non-interactive use.  If so, and if we are concerned about a message (error or
not) when not used interactively, then we can add a MSGP optional arg etc.  The
same holds for some of the other commands here.

I think it's good the way I defined it (show an error msg if no registers), but
I don't feel strongly about it at all.  I do think it's a bit silly to create a
window or frame showing an empty `*Output*' buffer.)

> `list-processes' says nothing even if no child process is.
> `list-directory' says nothing even if the directory given as 
> argument is empty.

FWIW, I don't see either of those as very comparable to `list-registers'.

Certainly not the Dired case.  You can work in an empty directory, doing lots of
things (including creating files and subdirs, search below in multiple subdirs,
etc.).