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.\" Copyright (c) 2003 Mike Barcroft <mike@FreeBSD.org>
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.\" $FreeBSD: src/lib/libc/gen/fpclassify.3,v 1.6 2005/01/27 05:46:16 das Exp $
.\"
.Dd $Mdocdate: July 29 2008 $
.Dt FPCLASSIFY 3
.Os
.Sh NAME
.Nm fpclassify ,
.Nm isfinite ,
.Nm isinf ,
.Nm isnan ,
.Nm isnormal ,
.Nm signbit
.Nd classify a floating-point number
.Sh SYNOPSIS
.In math.h
.Ft int
.Fn fpclassify "real-floating x"
.Ft int
.Fn isfinite "real-floating x"
.Ft int
.Fn isinf "real-floating x"
.Ft int
.Fn isnan "real-floating x"
.Ft int
.Fn isnormal "real-floating x"
.Ft int
.Fn signbit "real-floating x"
.Sh DESCRIPTION
The
.Fn fpclassify
macro takes an argument of
.Fa x
and returns one of the following manifest constants:
.Pp
.Bl -tag -width "FP_SUBNORMALXXX" -offset indent -compact
.It Dv FP_INFINITE
Indicates that
.Fa x
is an infinite number.
.It Dv FP_NAN
Indicates that
.Fa x
is not a number (NaN).
.It Dv FP_NORMAL
Indicates that
.Fa x
is a normalized number.
.It Dv FP_SUBNORMAL
Indicates that
.Fa x
is a denormalized number.
.It Dv FP_ZERO
Indicates that
.Fa x
is zero (0 or \-0).
.El
.Pp
The
.Fn isfinite
macro returns a non-zero value if and only if its argument has
a finite (zero, subnormal, or normal) value.
.Pp
The
.Fn isinf ,
.Fn isnan ,
and
.Fn isnormal
macros return non-zero if and only if
.Fa x
is an infinity, NaN,
or a non-zero normalized number, respectively.
.Pp
The
.Fn signbit
macro takes an argument of
.Fa x
and returns non-zero if the value of its sign is negative, otherwise 0.
.Sh SEE ALSO
.Xr isgreater 3 ,
.Xr math 3
.Sh STANDARDS
The
.Fn fpclassify ,
.Fn isfinite ,
.Fn isinf ,
.Fn isnan ,
.Fn isnormal ,
and
.Fn signbit
macros conform to
.St -isoC-99 .
.Pp
The symbols
.Fn isinff ,
and
.Fn isnanf
are provided as compatibility aliases to
.Fn isinf ,
and
.Fn isnan ,
respectively, and their uses are deprecated.
Similarly,
.Fn finite
and
.Fn finitef
are deprecated versions of
.Fn isfinite .
.Sh HISTORY
The
.Fn fpclassify ,
.Fn isfinite ,
.Fn isinf ,
.Fn isnan ,
.Fn isnormal ,
and
.Fn signbit
macros were added in
.Ox 4.4 .
.Bx 3
introduced
.Fn isinf
and
.Fn isnan
functions, which accepted
.Vt double
arguments; these have been superseded by the macros
described above.
.Sh BUGS
.Tn VAX
floating point does not have distinguished values
for either infinity or not-a-number.
.Fn isinf ,
.Fn isinff ,
.Fn isnan ,
and
.Fn isnanf
routines always return 0 on that architecture.
Similarly,
.Fn finite ,
and
.Fn isfinite
always return 1.