mirror of https://github.com/mkerrisk/man-pages
74 lines
2.0 KiB
Groff
74 lines
2.0 KiB
Groff
.\" Copyright 1995 Jim Van Zandt <jrv@vanzandt.mv.com>
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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.\" manual page may be incorrect or out-of-date.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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.\"
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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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.\" Modified 2002-07-27 by Walter Harms
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.\" (walter.harms@informatik.uni-oldenburg.de)
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.TH LOG1P 3 2007-07-26 "" "Linux Programmer's Manual"
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.SH NAME
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log1p, log1pf, log1pl \- logarithm of 1 plus argument
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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 "double log1p(double " x );
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.br
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.BI "float log1pf(float " x );
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.br
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.BI "long double log1pl(long double " x );
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.sp
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.fi
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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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.ad l
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.BR log1p (),
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.BR log1pf (),
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.BR log1pl ():
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_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 500 || _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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.I log1p(x)
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returns a value equivalent to
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.nf
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log (1 + \fIx\fP)
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.fi
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It is computed in a way
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that is accurate even if the value of \fIx\fP is near zero.
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.SH "CONFORMING TO"
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BSD, C99.
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The
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.I float
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and
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.I "long double"
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variants are C99 requirements.
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.SH "SEE ALSO"
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.BR exp (3),
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.BR expm1 (3),
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.BR log (3)
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