mirror of https://github.com/mkerrisk/man-pages
115 lines
2.3 KiB
Groff
115 lines
2.3 KiB
Groff
.\" 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 2007-07-26 "" "Linux Programmer's Manual"
|
|
.SH NAME
|
|
fpclassify, isfinite, isnormal, isnan, isinf \- 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
|
|
Link with \fI\-lm\fP.
|
|
.sp
|
|
.in -4n
|
|
Feature Test Macro Requirements for glibc (see
|
|
.BR feature_test_macros (7)):
|
|
.in
|
|
.sp
|
|
.\" I haven't fully grokked the source to determine the FTM requirements;
|
|
.\" in part, the following has been tested by experiment.
|
|
.ad l
|
|
.BR fpclassify (),
|
|
.BR isfinite (),
|
|
.BR isnormal ():
|
|
_XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE; or
|
|
.I cc\ -std=c99
|
|
.br
|
|
.BR isnan ():
|
|
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE || _ISOC99_SOURCE; or
|
|
.I cc\ -std=c99
|
|
.br
|
|
.BR isinf ():
|
|
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE; or
|
|
.I cc\ -std=c99
|
|
.ad b
|
|
.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 is one of the following values:
|
|
.TP
|
|
.B FP_NAN
|
|
.I x
|
|
is "Not a Number".
|
|
.TP
|
|
.B FP_INFINITE
|
|
.I x
|
|
is either plus or minus infinity.
|
|
.TP
|
|
.B FP_ZERO
|
|
.I x
|
|
is zero.
|
|
.TP
|
|
.B FP_SUBNORMAL
|
|
.I x
|
|
is too small to be represented in normalized format.
|
|
.TP
|
|
.B FP_NORMAL
|
|
if nothing of the above is correct then 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 "CONFORMING TO"
|
|
C99
|
|
.SH NOTES
|
|
In glibc 2.01 and earlier,
|
|
.BR isinf ()
|
|
returns a non-zero value (actually: 1) if
|
|
.I x
|
|
is an infinity (positive or negative).
|
|
(This is all that C99 requires.)
|
|
.SH "SEE ALSO"
|
|
.BR finite (3),
|
|
.BR INFINITY (3),
|
|
.BR isgreater (3)
|
|
|