system. Since it is very simple, I will digress briefly from Lisp and
describe it here.
-@c GNU Emacs 24 in src/editfns.c
-@c the DEFUN for delete-and-extract-region
-
@need 1500
Like many of the other Emacs primitives,
@code{delete-and-extract-region} is written as an instance of a C
macro, a macro being a template for code. The complete macro looks
like this:
+@c This is a copy of editfns.c's DEFUN for delete-and-extract-region.
@smallexample
@group
DEFUN ("delete-and-extract-region", Fdelete_and_extract_region,
Sdelete_and_extract_region, 2, 2, 0,
doc: /* Delete the text between START and END and return it. */)
- (Lisp_Object start, Lisp_Object end)
+ (Lisp_Object start, Lisp_Object end)
@{
validate_region (&start, &end);
- if (XINT (start) == XINT (end))
+ if (XFIXNUM (start) == XFIXNUM (end))
return empty_unibyte_string;
- return del_range_1 (XINT (start), XINT (end), 1, 1);
+ return del_range_1 (XFIXNUM (start), XFIXNUM (end), 1, 1);
@}
@end group
@end smallexample
@smallexample
@group
validate_region (&start, &end);
-if (XINT (start) == XINT (end))
+if (XFIXNUM (start) == XFIXNUM (end))
return empty_unibyte_string;
-return del_range_1 (XINT (start), XINT (end), 1, 1);
+return del_range_1 (XFIXNUM (start), XFIXNUM (end), 1, 1);
@end group
@end smallexample
The @code{del_range_1} function actually deletes the text. It is a
complex function we will not look into. It updates the buffer and
does other things. However, it is worth looking at the two arguments
-passed to @code{del_range_1}. These are @w{@code{XINT (start)}} and
-@w{@code{XINT (end)}}.
+passed to @code{del_range_1}. These are @w{@code{XFIXNUM (start)}} and
+@w{@code{XFIXNUM (end)}}.
As far as the C language is concerned, @code{start} and @code{end} are
-two integers that mark the beginning and end of the region to be
-deleted@footnote{More precisely, and requiring more expert knowledge
-to understand, the two integers are of type @code{Lisp_Object}, which can
-also be a C union instead of an integer type.}.
+two opaque values that mark the beginning and end of the region to be
+deleted. More precisely, and requiring more expert knowledge
+to understand, the two values are of type @code{Lisp_Object}, which
+might be a C pointer, a C integer, or a C @code{struct}; C code
+ordinarily should not care how @code{Lisp_Object} is implemented.
-Integer widths depend on the machine, and are typically 32 or 64 bits.
-A few of the bits are used to specify the type of information; the
-remaining bits are used as content.
+@code{Lisp_Object} widths depend on the machine, and are typically 32
+or 64 bits. A few of the bits are used to specify the type of
+information; the remaining bits are used as content.
-@samp{XINT} is a C macro that extracts the relevant number from the
+@samp{XFIXNUM} is a C macro that extracts the relevant integer from the
longer collection of bits; the type bits are discarded.
@need 800
The command in @code{delete-and-extract-region} looks like this:
@smallexample
-del_range_1 (XINT (start), XINT (end), 1, 1);
+del_range_1 (XFIXNUM (start), XFIXNUM (end), 1, 1);
@end smallexample
@noindent
This can be useful after reducing the value of `message-log-max'."
(with-current-buffer (messages-buffer)
;; This is a reimplementation of this part of message_dolog() in xdisp.c:
- ;; if (NATNUMP (Vmessage_log_max))
+ ;; if (FIXNATP (Vmessage_log_max))
;; {
;; scan_newline (Z, Z_BYTE, BEG, BEG_BYTE,
- ;; -XFASTINT (Vmessage_log_max) - 1, 0);
- ;; del_range_both (BEG, BEG_BYTE, PT, PT_BYTE, 0);
+ ;; -XFIXNAT (Vmessage_log_max) - 1, false);
+ ;; del_range_both (BEG, BEG_BYTE, PT, PT_BYTE, false);
;; }
- (when (and (integerp message-log-max) (>= message-log-max 0))
+ (when (natnump message-log-max)
(let ((begin (point-min))
(end (save-excursion
(goto-char (point-max))
itype = ival >> (0 if USE_LSB_TAG else VALBITS)
itype = itype & ((1 << GCTYPEBITS) - 1)
- # For a Lisp integer N, yield "make_number(N)".
+ # For a Lisp fixnum N, yield "make_fixnum(N)".
if itype == Lisp_Int0 or itype == Lisp_Int1:
if USE_LSB_TAG:
ival = ival >> (GCTYPEBITS - 1)
ival = ival | (-1 << VALBITS)
else:
ival = ival & ((1 << VALBITS) - 1)
- return "make_number(%d)" % ival
+ return "make_fixnum(%d)" % ival
# For non-integers other than nil yield "XIL(N)", where N is a C integer.
# This helps humans distinguish Lisp_Object values from ordinary