Re: [External] : Re: Regexp for matching control character, say, FORM FEED. (Was: Re: The `^L' appeared in built-in help.)

[Hongyi Zhao <hongyi.zhao@gmail.com>]

On Thu, Jul 22, 2021 at 11:01 PM <tomas@tuxteam.de> wrote:
>
> On Thu, Jul 22, 2021 at 10:53:53PM +0800, Hongyi Zhao wrote:
> > On Thu, Jul 22, 2021 at 10:38 PM <tomas@tuxteam.de> wrote:
> > >
> > > On Thu, Jul 22, 2021 at 09:56:09PM +0800, Hongyi Zhao wrote:
> > >
> > > [...]
> > >
> > > > Suppose I've the following content in scratch buffer:
> > > >
> > > > (re-search-forward "\f")
> > > > ^L
> > > >
> > > > I put the point at the end of sexp line, and hit `C-j' to evaluate it.
> > > > I find that each time after the sexp has been evaluated successfully,
> > > > the `^L' line will be moved to the next line. See the screenshot in
> > > > the attachment, where I've evaluated the sexp 4 times.
> > > >
> > > > Any hints for this behavior?
> > >
> > > That depends on what C-j is bound to. What does say "describe-key",
> > > aka C-h C-k?
> >
> > `C-h k C-j RET':
> > ;;;
> > C-j runs the command eval-print-last-sexp (found in
> > lisp-interaction-mode-map), which is an interactive compiled Lisp
> > function in ‘elisp-mode.el’.
>
> Ah. You seem to be in a "lisp interaction" buffer.

I'm in scratch buffer, and the "lisp interaction" is its default major mode.

> Then it's clear:
> it's the `print' part of `eval-print-last-sexp' what is inserting
> stuff in your buffer: the value of (re-search-forward "\f").
>
> Before it does a newline (that is what moves the ^L forward), then the
> searching and moving of point happens, then (you should see that, too,
> the expression's value (point's position, an integer) is inserted: you
> should get a number after the ^L, too.

Thank you for your explanation.

Best,
HY