Re: Suggestion: Simple way to make conditional key bindings.

[Richard Stallman <rms@gnu.org>]

    (global-set-key [f11] 
		    '(cond
		      (a delete-char)
		      (b find-file)
		      (c nil)
		      (t (keymap (?a . "abc") (?b . "bcd")))))

I agree that this is convenient.  The question is, is it better to
make this a primitive facility, as you suggested, or to add a macro to
do the job using menu-item, as Stefan suggested?

Using menu-item has an advantage that we use a function rather than
a form.  It also has the advantage of not adding any complexity
to the key binding data structures.

But those are not the only factors; others may be more important.

    One advantage (IMO) is that C-h k C-y will report yank or
    yank-with-properties depending on the actual function taken if
    you hit C-y.

If we use menu-item, what will C-h c say? 

    One problem with your change is "what binding do we use when we don't want
    to run code?".  The `menu-item' syntax provides a binding (in the example
    above it's "my-filter" which is not very useful indeed) for the case
    where code should not be evalled (for example in `where-is').

I think we do want where-is to find this binding, though.

      (define-key global-map "\C-y" 'yank-careful)
      (defun yank-careful (...)
	"Reinsert the last stretch of killed text, like `yank'.
      Contrary to `yank' this function is careful to preserve some important
      text properties when yanking tables."
	...)

    The advantage is that C-h k C-y doesn't just give you one of the two
    bindings but a docstring that describes both.

I think that sometimes this will be better, but sometimes it will be
better for C-h k to give the doc string for the specific command
that will be executed.