(/ N) now returns the reciprocal of N

This is more compatible with Common Lisp and XEmacs (Bug#21690).  See:
http://lists.gnu.org/archive/html/emacs-devel/2015-10/msg01053.html
* lisp/color.el (color-hue-to-rgb, color-hsl-to-rgb)
(color-xyz-to-srgb, color-xyz-to-lab):
* lisp/emacs-lisp/cl-extra.el (cl-float-limits):
* lisp/net/shr-color.el (shr-color-hue-to-rgb)
(shr-color-hsl-to-rgb-fractions):
Exploit the change to simplify the code a bit.
* lisp/emacs-lisp/bytecomp.el (byte-compile-quo):
Don’t complain about single-argument calls to ‘/’.
* src/data.c (arith_driver, float_arith_driver):
Implement the change.

1 files changed, 7 insertions, 4 deletions

diff --git a/src/data.c b/src/data.c
index b85d8a77106..33fe2855c99 100644
--- a/src/data.c
+++ b/src/data.c
@@ -2603,6 +2603,7 @@ arith_driver (enum arithop code, ptrdiff_t nargs, Lisp_Object *args)
       accum = 0;
       break;
     case Amult:
+    case Adiv:
       accum = 1;
       break;
     case Alogand:
@@ -2658,7 +2659,7 @@ arith_driver (enum arithop code, ptrdiff_t nargs, Lisp_Object *args)
             accum *= next;
           break;
         case Adiv:
-          if (!argnum)
+          if (! (argnum || nargs == 1))
             accum = next;
           else
             {
@@ -2727,7 +2728,7 @@ float_arith_driver (double accum, ptrdiff_t argnum, enum arithop code,
           accum *= next;
           break;
         case Adiv:
-          if (!argnum)
+          if (! (argnum || nargs == 1))
             accum = next;
           else
             {
@@ -2782,9 +2783,11 @@ usage: (* &rest NUMBERS-OR-MARKERS)  */)
 }
 
 DEFUN ("/", Fquo, Squo, 1, MANY, 0,
-       doc: /* Return first argument divided by all the remaining arguments.
+       doc: /* Divide number by divisors and return the result.
+With two or more arguments, return first argument divided by the rest.
+With one argument, return 1 divided by the argument.
 The arguments must be numbers or markers.
-usage: (/ DIVIDEND &rest DIVISORS)  */)
+usage: (/ NUMBER &rest DIVISORS)  */)
   (ptrdiff_t nargs, Lisp_Object *args)
 {
   ptrdiff_t argnum;