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.\" 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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2007-04-12 22:42:49 +00:00
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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.\" manual page may be incorrect or out-of-date.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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2007-04-12 22:42:49 +00:00
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.\"
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2004-11-03 13:51:07 +00:00
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\"
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2007-07-08 12:11:40 +00:00
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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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getresuid.2, mremap.2, poll.2, remap_file_pages.2, setresuid.2, splice.2, sync_file_range.2, syscall.2, tee.2, vmsplice.2, INFINITY.3, aio_init.3, asprintf.3, assert_perror.3, basename.3, bsd_signal.3, canonicalize_file_name.3, clog10.3, crypt.3, dl_iterate_phdr.3, dlopen.3, encrypt.3, exp10.3, fcloseall.3, fenv.3, fopencookie.3, ftw.3, getaddrinfo_a.3, getloadavg.3, getutent.3, grantpt.3, hsearch.3, lseek64.3, memmem.3, mempcpy.3, pow10.3, program_invocation_name.3, ptsname.3, putgrent.3, sched_getcpu.3, sincos.3, strchr.3, strfry.3, strnlen.3, strptime.3, strstr.3, strverscmp.3, swab.3, sysv_signal.3, tsearch.3, unlockpt.3, wcwidth.3: Add reference to feature_test_macros(7)
Some pages simply list feature test macro requirements in
the form:
#define #GNU_SOURCE
#include <someheader.h>
For these pages, add a "See feature_test_macros(7)" comment
on the "#define" line.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2010-10-31 04:31:47 +00:00
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.BR "#define _ISOC99_SOURCE" " /* See feature_test_macros(7) */"
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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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2007-05-19 04:30:20 +00:00
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.SH "CONFORMING TO"
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2008-07-15 13:39:17 +00:00
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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 math_error (7)
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