2004-11-03 13:51:07 +00:00
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.\" Copyright 2002 Walter Harms (walter.harms@informatik.uni-oldenburg.de)
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.\" Distributed under GPL
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.\" Based on glibc infopages
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.\"
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.\" Corrections by aeb
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2008-08-11 17:13:47 +00:00
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.TH NAN 3 2008-08-11 "GNU" "Linux Programmer's Manual"
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2004-11-03 13:51:07 +00:00
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.SH NAME
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nan, nanf, nanl \- return 'Not a Number'
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.SH SYNOPSIS
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.B #include <math.h>
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.sp
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.BI "double nan(const char *" tagp );
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.br
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.BI "float nanf(const char *" tagp );
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.br
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2004-11-03 13:51:07 +00:00
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.BI "long double nanl(const char *" tagp );
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.sp
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2008-07-23 13:04:35 +00:00
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Link with \fI\-lm\fP.
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2007-07-08 12:11:40 +00:00
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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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.BR nan (),
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2007-07-08 12:39:24 +00:00
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.BR nanf (),
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2007-07-08 12:11:40 +00:00
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.BR nanl ():
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_XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE; or
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.I cc\ -std=c99
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.SH DESCRIPTION
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These functions return a representation (determined by
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.IR tagp )
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of a quiet NaN.
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If the implementation does not support
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2004-11-03 13:51:07 +00:00
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quiet NaNs, these functions return zero.
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.LP
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The call
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.I nan("char-sequence")
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is equivalent to:
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.nf
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strtod("NAN(char-sequence)", NULL);
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.fi
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.PP
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Similarly, calls to
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2005-11-02 11:34:24 +00:00
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.BR nanf ()
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and
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.BR nanl ()
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are equivalent to analogous calls to
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2007-05-12 00:30:29 +00:00
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.BR strtof (3)
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2004-11-03 13:51:07 +00:00
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and
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2007-05-12 00:30:29 +00:00
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.BR strtold (3).
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2004-11-03 13:51:07 +00:00
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.PP
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The argument
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.I tagp
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2007-04-12 22:42:49 +00:00
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is used in an unspecified manner.
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On IEEE 754 systems, there are many representations of NaN, and
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.I tagp
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selects one.
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On other systems it may do nothing.
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.SH VERSIONS
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These functions first appeared in glibc in version 2.1.
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.SH "CONFORMING TO"
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2008-07-25 20:21:06 +00:00
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C99, POSIX.1-2001.
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See also IEC 559 and the appendix with
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recommended functions in IEEE 754/IEEE 854.
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.SH "SEE ALSO"
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.BR isnan (3),
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2008-07-23 13:04:35 +00:00
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.BR strtod (3),
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.BR math_error (7)
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