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Re: reading the C source of Emacs
From: |
Oliver Scholz |
Subject: |
Re: reading the C source of Emacs |
Date: |
Fri, 17 Jan 2003 05:55:40 +0100 |
User-agent: |
Gnus/5.090008 (Oort Gnus v0.08) Emacs/21.2 (i386-msvc-nt5.1.2600) |
Thank you all for you advice. You helped to set me on the track. But
it is indeed a rather difficult read for me. My head dizzles is still
a bit dizzling.
Below are my very first steps in C: a version of `find-if' as a
starter. I'd appreciate any comment. (Did I miss something important,
for example?)
One thing that I noticed is that my `find-if' causes an infinite loop,
when applied to a recursive (?) list, à la:
(setq my-list (list 'alpha 'beta 'gamma))
(setcdr (cddr my-list) my-list)
(find-if (lambda (elt) (eq elt 'zeta)) my-list)
I couldn't think of a remedy for this. How could I solve this problem?
OTOH this happens to `copy-sequence', too. So maybe this is o.k.?
Index: src/fns.c
===================================================================
RCS file: /cvsroot/emacs/emacs/src/fns.c,v
retrieving revision 1.327
diff -u -r1.327 fns.c
--- src/fns.c 6 Jan 2003 15:41:17 -0000 1.327
+++ src/fns.c 17 Jan 2003 04:35:26 -0000
@@ -2913,6 +2913,57 @@
return sequence;
}
+
+#define FIND_IF_1(VARIABLE, PREDICATE, ELEMENT) \
+ if (! NILP (call1 ((PREDICATE), (ELEMENT)))) \
+ { \
+ (VARIABLE) = (ELEMENT); \
+ break; \
+ }
+
+DEFUN ("find-if", Ffind_if, Sfind_if, 2, 2, 0,
+ doc: /* Return the first element for which PREDICATE returns non-nil.
*/)
+ (predicate, sequence)
+ Lisp_Object predicate, sequence;
+{
+ Lisp_Object elt = Qnil;
+
+ if (STRINGP (sequence))
+ {
+ int nchars = SCHARS (sequence);
+ int cidx, bidx;
+
+ for (cidx = bidx = 0; cidx < nchars;)
+ {
+ int c;
+ FETCH_STRING_CHAR_ADVANCE (c, sequence, cidx, bidx);
+ FIND_IF_1 (elt, predicate, (make_number (c)));
+ QUIT;
+ }}
+ else if (VECTORP (sequence))
+ {
+ int i;
+ int len = ASIZE (sequence);
+
+ for (i = 0; i < len; i++)
+ FIND_IF_1 (elt, predicate, (AREF (sequence, i)));
+ QUIT;
+ }
+ else /* It ought to be a list. */
+ {
+ while (! NILP (sequence))
+ {
+ if (! (CONSP (sequence)))
+ return wrong_type_argument (Qsequencep, sequence);
+ else FIND_IF_1 (elt, predicate, (XCAR (sequence)));
+ sequence = XCDR (sequence);
+ QUIT;
+ }}
+ return elt;
+}
+
+
+
/* Anything that calls this function must protect from GC! */
@@ -5580,6 +5631,8 @@
defsubr (&Snconc);
defsubr (&Smapcar);
defsubr (&Smapc);
+ // defsubr (&Sexplode);
+ defsubr (&Sfind_if);
defsubr (&Smapconcat);
defsubr (&Sy_or_n_p);
defsubr (&Syes_or_no_p);
Oliver
--
28 Nivôse an 211 de la Révolution
Liberté, Egalité, Fraternité!
- Re: reading the C source of Emacs, (continued)
Re: reading the C source of Emacs, Janusz S. Bień, 2003/01/13
Message not available
Re: reading the C source of Emacs, Stefan Monnier <address@hidden>, 2003/01/13
- Re: reading the C source of Emacs,
Oliver Scholz <=