[src/trunk]: src/lib/libc/gen move VAX notes to CAVEATS, clarify.

[maya <maya%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/73d355bcd18e
branches:  trunk
changeset: 826757:73d355bcd18e
user:      maya <maya%NetBSD.org@localhost>
date:      Wed Sep 27 18:55:50 2017 +0000

description:
move VAX notes to CAVEATS, clarify.

diffstat:

 lib/libc/gen/isnan.3 |  15 +++++++--------
 1 files changed, 7 insertions(+), 8 deletions(-)

diffs (40 lines):

diff -r 3cafc8baed8f -r 73d355bcd18e lib/libc/gen/isnan.3
--- a/lib/libc/gen/isnan.3      Wed Sep 27 10:50:06 2017 +0000
+++ b/lib/libc/gen/isnan.3      Wed Sep 27 18:55:50 2017 +0000
@@ -1,4 +1,4 @@
-.\"    $NetBSD: isnan.3,v 1.2 2004/03/04 23:49:31 wiz Exp $
+.\"    $NetBSD: isnan.3,v 1.3 2017/09/27 18:55:50 maya Exp $
 .\"
 .\" Copyright (c) 1991, 1993
 .\"    The Regents of the University of California.  All rights reserved.
@@ -30,7 +30,7 @@
 .\"     From: @(#)isinf.3      8.2 (Berkeley) 1/29/94
 .\"    from: NetBSD: isinf.3,v 1.10 2003/08/07 16:42:52 agc Exp
 .\"
-.Dd March 5, 2004
+.Dd September 27, 2017
 .Dt ISNAN 3
 .Os
 .Sh NAME
@@ -52,12 +52,6 @@
 An argument represented in a format wider than its semantic type is
 converted to its semantic type first.
 The determination is then based on the type of the argument.
-.Ss IEEE 754
-It is determined whether the value of
-.Fa x
-is a NaN.
-.Ss VAX
-NaNs are not supported.
 .Sh RETURN VALUES
 The
 .Fn isnan
@@ -84,3 +78,8 @@
 .Fn isnan
 macro conforms to
 .St -isoC-99 .
+.Sh CAVEATS
+On VAX the
+.Fn isnan
+function always returns 0,
+as the architecture doesn't support NaN.