(nnmail-extra-headers): Add defvar.

[gnu-emacs] / lispref / numbers.texi

diff --git a/lispref/numbers.texi b/lispref/numbers.texi
index 776251e4933156f55788a07b0ce2769104a40343..db28a2850a6afd6b145acee34d695a4cead1d8cd 100644 (file)
--- a/lispref/numbers.texi
+++ b/lispref/numbers.texi
@@ -1,7 +1,7 @@
 @c -*-texinfo-*-
 @c This is part of the GNU Emacs Lisp Reference Manual.
 @c -*-texinfo-*-
 @c This is part of the GNU Emacs Lisp Reference Manual.

-@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2003
-@c   Free Software Foundation, Inc.
+@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2002, 2003,
+@c   2004, 2005 Free Software Foundation, Inc.

 @c See the file elisp.texi for copying conditions.
 @setfilename ../info/numbers
 @node Numbers, Strings and Characters, Lisp Data Types, Top
 @c See the file elisp.texi for copying conditions.
 @setfilename ../info/numbers
 @node Numbers, Strings and Characters, Lisp Data Types, Top


@@ -183,21 +183,26 @@ there is no correct answer.  For example, @code{(/ 0.0 0.0)} returns a
 NaN.  For practical purposes, there's no significant difference between
 different NaN values in Emacs Lisp, and there's no rule for precisely
 which NaN value should be used in a particular case, so Emacs Lisp
 NaN.  For practical purposes, there's no significant difference between
 different NaN values in Emacs Lisp, and there's no rule for precisely
 which NaN value should be used in a particular case, so Emacs Lisp

-doesn't try to distinguish them.  Here are the read syntaxes for
-these special floating point values:
+doesn't try to distinguish them (but it does report the sign, if you
+print it).  Here are the read syntaxes for these special floating
+point values:

 
 @table @asis
 @item positive infinity
 @samp{1.0e+INF}
 @item negative infinity
 @samp{-1.0e+INF}
 
 @table @asis
 @item positive infinity
 @samp{1.0e+INF}
 @item negative infinity
 @samp{-1.0e+INF}

-@item Not-a-number
-@samp{0.0e+NaN}.
+@item Not-a-number 
+@samp{0.0e+NaN} or @samp{-0.0e+NaN}.

 @end table
 
 @end table
 

-  In addition, the value @code{-0.0} is distinguishable from ordinary
-zero in @acronym{IEEE} floating point (although @code{equal} and
-@code{=} consider them equal values).
+  To test whether a floating point value is a NaN, compare it with
+itself using @code{=}.  That returns @code{nil} for a NaN, and
+@code{t} for any other floating point value.
+
+  The value @code{-0.0} is distinguishable from ordinary zero in
+@acronym{IEEE} floating point, but Emacs Lisp @code{equal} and
+@code{=} consider them equal values.

 
   You can use @code{logb} to extract the binary exponent of a floating
 point number (or estimate the logarithm of an integer):
 
   You can use @code{logb} to extract the binary exponent of a floating
 point number (or estimate the logarithm of an integer):