Re: comint-carriage-motion causes severe problems.

[Stefan Monnier]

> address@hidden (Kai Großjohann) writes:
> > It seems, however, that M-x ielm RET should lead to a buffer where
> > comint-carriage-motion is off.  Is there a way to do that?
> 
> I guess it could be done by having ielm make
> `comint-output-filter-functions' a buffer-local copy of the global value,
> excluding `comint-carriage-motion'.

But we need to be careful that this local copy does not contain t.
And if the global hook is modified afterwards, the local copy will not
see the change.

> `remove-hook' actually contains commented-out code that would do this sort
> of thing more elegantly, by adding a local `not'-hook that would
> effectively override a global hook.  I don't know why that code is
> commented out; perhaps it doesn't work.

Because it requires support in the C code that I have not installed (yet)
because I haven't felt like arguing about its usefulness.


        Stefan


Index: eval.c
===================================================================
RCS file: /cvsroot/emacs/emacs/src/eval.c,v
retrieving revision 1.189
diff -u -r1.189 eval.c
--- eval.c      28 May 2002 20:24:32 -0000      1.189
+++ eval.c      2 Jul 2002 15:30:55 -0000
@@ -90,7 +90,7 @@
 Lisp_Object Qautoload, Qmacro, Qexit, Qinteractive, Qcommandp, Qdefun;
 Lisp_Object Qinhibit_quit, Vinhibit_quit, Vquit_flag;
 Lisp_Object Qand_rest, Qand_optional;
-Lisp_Object Qdebug_on_error;
+Lisp_Object Qdebug_on_error, Qnot;
 Lisp_Object Qdeclare;
 
 /* This holds either the symbol `run-hooks' or nil.
@@ -2338,7 +2366,8 @@
 {
   Lisp_Object sym, val, ret;
   Lisp_Object globals;
-  struct gcpro gcpro1, gcpro2, gcpro3;
+  Lisp_Object negatives = Qnil;
+  struct gcpro gcpro1, gcpro2, gcpro3, gcpro4;
 
   /* If we are dying or still initializing,
      don't do anything--it would probably crash if we tried.  */
@@ -2359,7 +2388,7 @@
   else
     {
       globals = Qnil;
-      GCPRO3 (sym, val, globals);
+      GCPRO4 (sym, val, globals, negatives);
 
       for (;
           CONSP (val) && ((cond == to_completion)
@@ -2381,10 +2410,15 @@
                  args[0] = XCAR (globals);
                  /* In a global value, t should not occur.  If it does, we
                     must ignore it to avoid an endless loop.  */
-                 if (!EQ (args[0], Qt))
+                 if (!(EQ (args[0], Qt))
+                     && NILP (Fmember (args[0], negatives)))
                    ret = Ffuncall (nargs, args);
                }
            }
+         else if (CONSP (XCAR (val)) && (EQ (XCAR (XCAR (val)), Qnot)))
+           /* (not . FUNCTION) indicates that any subsequent FUNCTION
+              should be ignored.  */
+           negatives = Fcons (XCDR (XCAR (val)), negatives);
          else
            {
              args[0] = XCAR (val);
@@ -3276,6 +3310,9 @@
   Qdebug_on_error = intern ("debug-on-error");
   staticpro (&Qdebug_on_error);
 
+  Qnot = intern ("not");
+  staticpro (&Qnot);
+
   Qmacro = intern ("macro");
   staticpro (&Qmacro);
 
Index: subr.el
===================================================================
RCS file: /cvsroot/emacs/emacs/lisp/subr.el,v
retrieving revision 1.311
diff -u -r1.311 subr.el
--- subr.el     27 Jun 2002 16:08:56 -0000      1.311
+++ subr.el     2 Jul 2002 15:32:59 -0000
@@ -58,6 +58,17 @@
 
 (defalias 'not 'null)
 
+(if (not (fboundp 'while))
+    (defmacro while (test &rest body)
+      "Like `until' except TEST is negated."
+      `(progn (until (not ,test) ,@body) nil)))
+(if (not (fboundp 'until))
+    (defmacro until (test &rest body)
+      "Like `while' except TEST is negated and the form returns non-nil."
+      `(let (-until-res)
+        (while (not (setq -until-res ,test)) ,@body)
+        -until-res)))
+
 (defmacro lambda (&rest cdr)
   "Return a lambda expression.
 A call of the form (lambda ARGS DOCSTRING INTERACTIVE BODY) is
@@ -833,9 +844,13 @@
        (if (equal hook-value function) (setq hook-value nil))
       (setq hook-value (delete function (copy-sequence hook-value))))
     ;; If the function is on the global hook, we need to shadow it locally
-    ;;(when (and local (member function (default-value hook))
-    ;;        (not (member (cons 'not function) hook-value)))
-    ;;  (push (cons 'not function) hook-value))
+    (when (and local (local-variable-if-set-p hook)
+              (member function
+                      (let ((val (default-value hook)))
+                        (if (or (not (listp val)) (functionp val))
+                            (list val) val)))
+              (not (member (cons 'not function) hook-value)))
+      (push (cons 'not function) hook-value))
     ;; Set the actual variable
     (if (not local)
        (set-default hook hook-value)