M-. vs C-h o

M-. vs C-h o

[Hongyi Zhao]

See the following returned info, with point indicated by | on mapc:

M-. map|c

DEFUN ("mapc", Fmapc, Smapc, 2, 2, 0,
       doc: /* Apply FUNCTION to each element of SEQUENCE for side effects only.
Unlike `mapcar', don't accumulate the results.  Return SEQUENCE.
SEQUENCE may be a list, a vector, a bool-vector, or a string.  */)


C-h o mapc RET

mapc is a built-in function in ‘src/fns.c’.

(mapc FUNCTION SEQUENCE)

Apply FUNCTION to each element of SEQUENCE for side effects only.
Unlike ‘mapcar’, don’t accumulate the results.  Return SEQUENCE.
SEQUENCE may be a list, a vector, a bool-vector, or a string.


So, I want to know the correspondence of the following two descriptions:

DEFUN ("mapc", Fmapc, Smapc, 2, 2, 0,

and

(mapc FUNCTION SEQUENCE)

Regards
-- 
Assoc. Prof. Hongyi Zhao <hongyi.zhao@gmail.com>
Theory and Simulation of Materials
Hebei Vocational University of Technology and Engineering
No. 473, Quannan West Street, Xindu District, Xingtai, Hebei province

Re: M-. vs C-h o

[Emanuel Berg via Users list for the GNU Emacs text editor]

Hongyi Zhao wrote:

> See the following returned info, with point indicated by | on mapc:
>
> M-. map|c
>
> DEFUN ("mapc", Fmapc, Smapc, 2, 2, 0,
>        doc: /* Apply FUNCTION to each element of SEQUENCE for side effects only.
> Unlike `mapcar', don't accumulate the results.  Return SEQUENCE.
> SEQUENCE may be a list, a vector, a bool-vector, or a string.  */)
>
> C-h o mapc RET
>
> mapc is a built-in function in ‘src/fns.c’.
>
> (mapc FUNCTION SEQUENCE)
>
> Apply FUNCTION to each element of SEQUENCE for side effects only.
> Unlike ‘mapcar’, don’t accumulate the results.  Return SEQUENCE.
> SEQUENCE may be a list, a vector, a bool-vector, or a string.
>
> So, I want to know the correspondence of the following two descriptions:
>
> DEFUN ("mapc", Fmapc, Smapc, 2, 2, 0,
>
> and
>
> (mapc FUNCTION SEQUENCE)

Not following?

-- 
underground experts united
https://dataswamp.org/~incal

RE: [External] : M-. vs C-h o

[Drew Adams]

> mapc is a built-in function in ‘src/fns.c’.

That tells you that it's a Lisp function that's
"built-in", meaning that it's implemented in C.
And it points you to the C definition in fns.c.

That C code provides the complete definition,
including the doc string.

> DEFUN ("mapc", Fmapc, Smapc, 2, 2, 0,

That tells you that Lisp function `mapc' is
defined using C definition Fmapc, and the
function takes two arguments.  Someone else
can provide or point you to more info about
this.

Re: [External] : M-. vs C-h o

[Emanuel Berg via Users list for the GNU Emacs text editor]

Drew Adams wrote:

>> mapc is a built-in function in ‘src/fns.c’.
>
> That tells you that it's a Lisp function that's "built-in",
> meaning that it's implemented in C.

A so-called Lisp primitive ...

"Lisp primitives are Lisp functions implemented in C"

http://www.gnu.org/software/emacs/manual/html_node/elisp/Writing-Emacs-Primitives.html
(info "(elisp)Writing Emacs Primitives")

-- 
underground experts united
https://dataswamp.org/~incal

Re: [External] : M-. vs C-h o

[Hongyi Zhao]

On Fri, Oct 22, 2021 at 9:18 AM Emanuel Berg via Users list for the
GNU Emacs text editor <help-gnu-emacs@gnu.org> wrote:
>
> Drew Adams wrote:
>
> >> mapc is a built-in function in ‘src/fns.c’.
> >
> > That tells you that it's a Lisp function that's "built-in",
> > meaning that it's implemented in C.
>
> A so-called Lisp primitive ...
>
> "Lisp primitives are Lisp functions implemented in C"
>
> http://www.gnu.org/software/emacs/manual/html_node/elisp/Writing-Emacs-Primitives.html
> (info "(elisp)Writing Emacs Primitives")

Thank you for pointing this out.  I've `rg'ed the local Emacs git
source code repo, and it seems still difficult to pinpoint the
corresponding C source code implementation of DEFUN.

HZ

Re: [External] : M-. vs C-h o

[Óscar Fuentes]

Hongyi Zhao <hongyi.zhao@gmail.com> writes:

> Thank you for pointing this out.  I've `rg'ed the local Emacs git
> source code repo, and it seems still difficult to pinpoint the
> corresponding C source code implementation of DEFUN.
>
> HZ

DEFUN is a macro. If you search for

#define DEFUN

you will find it in src/lisp.h

Re: [External] : M-. vs C-h o

[Hongyi Zhao]

On Fri, Oct 22, 2021 at 10:31 AM Óscar Fuentes <ofv@wanadoo.es> wrote:
>
> Hongyi Zhao <hongyi.zhao@gmail.com> writes:
>
> > Thank you for pointing this out.  I've `rg'ed the local Emacs git
> > source code repo, and it seems still difficult to pinpoint the
> > corresponding C source code implementation of DEFUN.
> >
> > HZ
>
> DEFUN is a macro. If you search for
>
> #define DEFUN
>
> you will find it in src/lisp.h

Do you mean the following search result?

$ rg -A17 -B27 -uu '#define DEFUN\(lname' src/
src/lisp.h
3022-/* Define a built-in function for calling from Lisp.
3023- `lname' should be the name to give the function in Lisp,
3024-    as a null-terminated C string.
3025- `fnname' should be the name of the function in C.
3026-    By convention, it starts with F.
3027- `sname' should be the name for the C constant structure
3028-    that records information on this function for internal use.
3029-    By convention, it should be the same as `fnname' but with S
instead of F.
3030-    It's too bad that C macros can't compute this from `fnname'.
3031- `minargs' should be a number, the minimum number of arguments allowed.
3032- `maxargs' should be a number, the maximum number of arguments allowed,
3033-    or else MANY or UNEVALLED.
3034-    MANY means pass a vector of evaluated arguments,
3035-     in the form of an integer number-of-arguments
3036-     followed by the address of a vector of Lisp_Objects
3037-     which contains the argument values.
3038-    UNEVALLED means pass the list of unevaluated arguments
3039- `intspec' says how interactive arguments are to be fetched.
3040-    If the string starts with a `(', `intspec' is evaluated and
the resulting
3041-    list is the list of arguments.
3042-    If it's a string that doesn't start with `(', the value should follow
3043-    the one of the doc string for `interactive'.
3044-    A null string means call interactively with no arguments.
3045- `doc' is documentation for the user.  */
3046-
3047-/* This version of DEFUN declares a function prototype with the right
3048-   arguments, so we can catch errors with maxargs at compile-time.  */
3049:#define DEFUN(lname, fnname, sname, minargs, maxargs, intspec, doc)    \
3050-  SUBR_SECTION_ATTRIBUTE                                                \
3051-  static union Aligned_Lisp_Subr sname =                                \
3052-     {{{ PVEC_SUBR << PSEUDOVECTOR_AREA_BITS },                \
3053-       { .a ## maxargs = fnname },                    \
3054-       minargs, maxargs, lname, {intspec}, 0}};                \
3055-   Lisp_Object fnname
3056-
3057-/* defsubr (Sname);
3058-   is how we define the symbol for function `name' at start-up time.  */
3059-extern void defsubr (union Aligned_Lisp_Subr *);
3060-
3061-enum maxargs
3062-  {
3063-    MANY = -2,
3064-    UNEVALLED = -1
3065-  };
3066-

HZ

Re: M-. vs C-h o

[Eli Zaretskii]

> From: Hongyi Zhao <hongyi.zhao@gmail.com>
> Date: Fri, 22 Oct 2021 08:28:48 +0800
> 
> So, I want to know the correspondence of the following two descriptions:
> 
> DEFUN ("mapc", Fmapc, Smapc, 2, 2, 0,
> 
> and
> 
> (mapc FUNCTION SEQUENCE)

'mapc' is a "primitive", i.e. a Lisp-callable function that's
implemented in C.  I suggest to read the node "Writing Emacs
Primitives" in the ELisp manual, it will explain that to you.

Re: M-. vs C-h o

[Hongyi Zhao]

On Fri, Oct 22, 2021 at 2:26 PM Eli Zaretskii <eliz@gnu.org> wrote:
>
> > From: Hongyi Zhao <hongyi.zhao@gmail.com>
> > Date: Fri, 22 Oct 2021 08:28:48 +0800
> >
> > So, I want to know the correspondence of the following two descriptions:
> >
> > DEFUN ("mapc", Fmapc, Smapc, 2, 2, 0,
> >
> > and
> >
> > (mapc FUNCTION SEQUENCE)
>
> 'mapc' is a "primitive", i.e. a Lisp-callable function that's
> implemented in C.  I suggest to read the node "Writing Emacs
> Primitives" in the ELisp manual, it will explain that to you.

Thank you. Emanuel Berg has told me the following:

(info "(elisp)Writing Emacs Primitives")

HZ