Add predicate proper-list-p

For discussion, see emacs-devel thread starting at
https://lists.gnu.org/archive/html/emacs-devel/2018-04/msg00460.html.

* lisp/subr.el (proper-list-p): New function.
Implementation suggested by Paul Eggert <eggert@cs.ucla.edu> in
https://lists.gnu.org/archive/html/emacs-devel/2018-06/msg00138.html.
* doc/lispref/lists.texi (List Elements):
* etc/NEWS: Document proper-list-p.
* lisp/org/ob-core.el (org-babel-insert-result):
* lisp/emacs-lisp/byte-opt.el (byte-optimize-if):
* lisp/emacs-lisp/cl-macs.el (cl--make-usage-args): Use proper-list-p.
* lisp/emacs-lisp/ert.el (ert--proper-list-p): Remove.
Replaced by proper-list-p in lisp/subr.el.
(ert--explain-equal-rec): Use proper-list-length.
* lisp/format.el (format-proper-list-p): Remove.
Replaced by proper-list-p in lisp/subr.el.
(format-annotate-single-property-change): Use proper-list-p.
* test/lisp/emacs-lisp/ert-tests.el (ert-test-proper-list-p):
Move from here...
* test/lisp/subr-tests.el (subr-tests--proper-list-length):
...to here, mutatis mutandis.

1 files changed, 2 insertions, 3 deletions

diff --git a/lisp/org/ob-core.el b/lisp/org/ob-core.el
index 5d5faaa6fd0..a5449fe35e9 100644
--- a/lisp/org/ob-core.el
+++ b/lisp/org/ob-core.el
@@ -2310,10 +2310,9 @@ INFO may provide the values of these header arguments (in the
                        (lambda (r)
                          ;; Non-nil when result R can be turned into
                          ;; a table.
-                         (and (listp r)
-                              (null (cdr (last r)))
+                         (and (proper-list-p r)
                               (cl-every
-                               (lambda (e) (or (atom e) (null (cdr (last e)))))
+                               (lambda (e) (or (atom e) (proper-list-p e)))
                                result)))))
                   ;; insert results based on type
                   (cond