.\" Copyright 2002 Walter Harms (walter.harms@informatik.uni-oldenburg.de)
.\" Distributed under GPL, 2002-07-27 Walter Harms
.\" This was done with the help of the glibc manual.
.\"
.\" 2004-10-31, aeb, corrected
.TH fpclassify 3  2004-10-31 "" "Linux Programmer's Manual"
.SH NAME
fpclassify, isfinite, isnormal, isnan \- floating-point classification macros
.SH SYNOPSIS
.nf
.B #include <math.h>
.sp
.BI "int fpclassify(" x );
.sp
.BI "int isfinite(" x );
.sp
.BI "int isnormal(" x );
.sp
.BI "int isnan(" x );
.sp
.BI "int isinf(" x );
.fi
.sp
Compile with \-std=c99; link with \-lm.
.SH DESCRIPTION
Floating point numbers can have special values, such as
infinite or NaN. With the macro
.BI fpclassify( x ) 
you can find out what type
.I x
is. The macro takes any floating-point expression as argument.
The result takes one of the following values: 
.TP
FP_NAN
.I x
is "Not a Number".
.TP
FP_INFINITE
.I x
is either plus or minus infinity.
.TP 
FP_ZERO
.I x
is zero.
.TP
FP_SUBNORMAL
.I x
is too small to be represented in normalized format.
.TP
FP_NORMAL
if nothing of the above is correct that it must be a
normal floating-point number.
.LP
The other macros provide a short answer to some standard questions.
.TP
.BI isfinite( x )
returns a non-zero value if
.br
(fpclassify(x) != FP_NAN && fpclassify(x) != FP_INFINITE)
.TP
.BI isnormal( x )
returns a non-zero value if
(fpclassify(x) == FP_NORMAL)
.TP
.BI isnan( x )
returns a non-zero value if
(fpclassify(x) == FP_NAN)
.TP
.BI isinf( x )
returns 1 if
.I x
is positive infinity, and \-1 if
.I x
is negative infinity.
.SH NOTE
In glibc 2.01 and earlier,
.B isinf()
returns a non-zero value (actually: 1) if
.I x
is an infinity (positive or negative).
(This is all that C99 requires.)
.SH "CONFORMING TO"
C99
.SH "SEE ALSO"
.BR finite (3),
.BR INFINITY (3),
.BR isgreater (3)