mirror of https://github.com/mkerrisk/man-pages
94 lines
2.4 KiB
Groff
94 lines
2.4 KiB
Groff
.\" Copyright 2004 Andries Brouwer <aeb@cwi.nl>.
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.\"
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\"
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.TH INFINITY 3 2007-07-26 "" "Linux Programmer's Manual"
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.SH NAME
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INFINITY, NAN, HUGE_VAL, HUGE_VALF, HUGE_VALL \- floating point constants
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.SH SYNOPSIS
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.nf
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.B #define _ISOC99_SOURCE
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.br
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.B #include <math.h>
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.sp
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.B INFINITY
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.sp
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.B NAN
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.sp
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.B HUGE_VAL
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.br
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.B HUGE_VALF
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.br
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.B HUGE_VALL
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.fi
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.SH DESCRIPTION
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The macro
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.B INFINITY
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expands to a \fIfloat\fP constant representing positive infinity.
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The macro
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.B NAN
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expands to a \fIfloat\fP constant representing a quiet NaN
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(when supported).
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A
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.I quiet
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NaN is a NaN ("not-a-number") that does not raise exceptions
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when it is used in arithmetic.
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The opposite is a
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.I signaling
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NaN.
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See IEC 60559:1989.
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The macros
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.BR HUGE_VAL ,
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.BR HUGE_VALF ,
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.B HUGE_VALL
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expand to constants of types \fIdouble\fP, \fIfloat\fP
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and \fIlong double\fP, respectively,
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that represent a large positive value, possibly plus infinity.
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.SH "CONFORMING TO"
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C99
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.SH AVAILABILITY
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On a glibc system, the macro
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.B HUGE_VAL
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is always available.
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Availability of the
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.B NAN
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macro can be tested using
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.BR "#ifdef NAN" ,
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and similarly for
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.BR INFINITY ,
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.BR HUGE_VALF ,
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.BR HUGE_VALL .
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They will be defined by
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.I <math.h>
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if
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.B _ISOC99_SOURCE
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or
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.B _GNU_SOURCE
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is defined, or
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.B __STDC_VERSION__
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is defined
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and has a value not less than 199901L.
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.SH "SEE ALSO"
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.BR fpclassify (3),
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.BR feature_test_macros (7)
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