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.TH isnan 3M "12 Jul 2006" "SunOS 5.11" "Mathematical Library Functions"
.SH NAME
isnan \- test for NaN
.SH SYNOPSIS
.LP
.nf
cc [ \fIflag\fR... ] \fIfile\fR... \fB-lm\fR [ \fIlibrary\fR... ]
#include <math.h>

\fBint\fR \fBisnan\fR(\fBdouble\fR \fIx\fR);
.fi

.LP
.nf
c99 [ \fIflag\fR... ] \fIfile\fR... \fB-lm\fR [ \fIlibrary\fR... ]
#include <math.h>

\fBint\fR \fBisnan\fR(\fBreal\(emfloating\fR \fIx\fR);
.fi

.SH DESCRIPTION
.sp
.LP
In C90 mode, the \fBisnan()\fR function tests whether \fIx\fR is NaN.
.sp
.LP
In C99 mode, the \fBisnan()\fR macro determines whether its argument value is
NaN. First, an argument represented in a format wider than its semantic type is
converted to its semantic type. The determination is then based on the type of
the argument.
.SH RETURN VALUES
.sp
.LP
Both the \fBisnan()\fR function and macro return non-zero if and only if
\fIx\fR is NaN.
.SH ERRORS
.sp
.LP
No errors are defined.
.SH WARNINGS
.sp
.LP
In C99 mode, the practice of explicitly supplying a prototype for \fBisnan()\fR
after the line
.sp
.in +2
.nf
#include <math.h>
.fi
.in -2

.sp
.LP
is obsolete and will no longer work.
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
tab() box;
cw(2.75i) |cw(2.75i) 
lw(2.75i) |lw(2.75i) 
.
ATTRIBUTE TYPEATTRIBUTE VALUE
_
Interface StabilityStandard
_
MT-LevelMT-Safe
.TE

.SH SEE ALSO
.sp
.LP
\fBfpclassify\fR(3M), \fBisfinite\fR(3M), \fBisinf\fR(3M), \fBisnormal\fR(3M),
\fBmath.h\fR(3HEAD), \fBsignbit\fR(3M), \fBattributes\fR(5), \fBstandards\fR(5)