mirror of https://github.com/mkerrisk/man-pages
114 lines
2.3 KiB
Groff
114 lines
2.3 KiB
Groff
.\" Copyright 2002 Walter Harms (walter.harms@informatik.uni-oldenburg.de)
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.\" Distributed under GPL, 2002-07-27 Walter Harms
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.\" This was done with the help of the glibc manual.
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.\"
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.\" 2004-10-31, aeb, corrected
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.TH FPCLASSIFY 3 2007-07-26 "" "Linux Programmer's Manual"
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.SH NAME
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fpclassify, isfinite, isnormal, isnan, isinf \- floating-point
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classification macros
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.SH SYNOPSIS
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.nf
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.B #include <math.h>
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.sp
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.BI "int fpclassify(" x );
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.sp
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.BI "int isfinite(" x );
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.sp
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.BI "int isnormal(" x );
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.sp
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.BI "int isnan(" x );
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.sp
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.BI "int isinf(" x );
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.fi
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.sp
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Link with \fI\-lm\fP.
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.sp
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.in -4n
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Feature Test Macro Requirements for glibc (see
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.BR feature_test_macros (7)):
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.in
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.sp
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.\" I haven't fully grokked the source to determine the FTM requirements;
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.\" in part, the following has been tested by experiment.
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.ad l
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.BR fpclassify (),
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.BR isfinite (),
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.BR isnormal ():
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_XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE; or
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.I cc\ -std=c99
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.br
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.BR isnan ():
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_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE || _ISOC99_SOURCE; or
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.I cc\ -std=c99
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.br
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.BR isinf ():
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_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE; or
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.I cc\ -std=c99
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.ad b
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.SH DESCRIPTION
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Floating point numbers can have special values, such as
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infinite or NaN.
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With the macro
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.BI fpclassify( x )
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you can find out what type
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.I x
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is.
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The macro takes any floating-point expression as argument.
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The result is one of the following values:
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.TP
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.B FP_NAN
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.I x
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is "Not a Number".
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.TP
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.B FP_INFINITE
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.I x
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is either plus or minus infinity.
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.TP
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.B FP_ZERO
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.I x
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is zero.
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.TP
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.B FP_SUBNORMAL
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.I x
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is too small to be represented in normalized format.
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.TP
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.B FP_NORMAL
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if nothing of the above is correct then it must be a
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normal floating-point number.
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.LP
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The other macros provide a short answer to some standard questions.
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.TP
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.BI isfinite( x )
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returns a non-zero value if
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.br
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(fpclassify(x) != FP_NAN && fpclassify(x) != FP_INFINITE)
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.TP
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.BI isnormal( x )
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returns a non-zero value if
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(fpclassify(x) == FP_NORMAL)
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.TP
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.BI isnan( x )
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returns a non-zero value if
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(fpclassify(x) == FP_NAN)
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.TP
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.BI isinf( x )
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returns 1 if
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.I x
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is positive infinity, and \-1 if
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.I x
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is negative infinity.
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.SH "CONFORMING TO"
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C99
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.SH NOTES
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In glibc 2.01 and earlier,
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.BR isinf ()
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returns a non-zero value (actually: 1) if
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.I x
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is an infinity (positive or negative).
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(This is all that C99 requires.)
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.SH "SEE ALSO"
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.BR finite (3),
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.BR INFINITY (3),
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.BR isgreater (3)
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