Re: Too fine design granularity leads to numerous macro/function/command existed in Emacs.

[Hongyi Zhao]

On Sat, Aug 14, 2021 at 2:19 PM Eli Zaretskii <eliz@gnu.org> wrote:
>
> > From: Hongyi Zhao <hongyi.zhao@gmail.com>
> > Date: Sat, 14 Aug 2021 08:46:27 +0800
> > Cc: help-gnu-emacs <help-gnu-emacs@gnu.org>
> >
> > > Specifically about the one example you provided: directory-files is a
> > > primitive, written in C, so it provides the basic functionality of
> > > fetching file names from a single directory. The
> > > directory-files-recursively function is written in Lisp, it builds on
> > > that primitive and provides extended functionality.
> >
> > Thank you for letting me know this difference, which I really didn't
> > notice before. But there's still one question I don't understand:
> > C is a compiled language, so how does the compilation and invocation
> > of such C primitives work in Emacs? Are they compiled into libraries
> > and called in real time?
>
> The low-level infrastructure of the Lisp machine

IMO, by saying ``Lisp machine'', it always means the operating system
is written in lisp, but this is obviously not the case of Emacs.

> in Emacs is also written in C, and that includes the primitives used to call 
> Lisp
> functions.  Those primitives have a special way of calling other
> primitives written in C.  Basically, a primitive written in C is
> wrapped in a special 'subr' object that tells Emacs about this, and
> then such primitives are called via the normal C mechanisms of calling
> functions.
>
> For more details, I suggest to study the node "Writing Emacs
> Primitives" in the ELisp manual.

Thank you very much for your valuable comments.

Hongyi