man3/log1p.3

   1 .\" Copyright 1995 Jim Van Zandt <jrv@vanzandt.mv.com>
   2 .\"
   3 .\" Permission is granted to make and distribute verbatim copies of this
   4 .\" manual provided the copyright notice and this permission notice are
   5 .\" preserved on all copies.
   6 .\"
   7 .\" Permission is granted to copy and distribute modified versions of this
   8 .\" manual under the conditions for verbatim copying, provided that the
   9 .\" entire resulting derived work is distributed under the terms of a
  10 .\" permission notice identical to this one.
  11 .\"
  12 .\" Since the Linux kernel and libraries are constantly changing, this
  13 .\" manual page may be incorrect or out-of-date.  The author(s) assume no
  14 .\" responsibility for errors or omissions, or for damages resulting from
  15 .\" the use of the information contained herein.  The author(s) may not
  16 .\" have taken the same level of care in the production of this manual,
  17 .\" which is licensed free of charge, as they might when working
  18 .\" professionally.
  19 .\"
  20 .\" Formatted or processed versions of this manual, if unaccompanied by
  21 .\" the source, must acknowledge the copyright and authors of this work.
  22 .\"
  23 .\" Modified 2002-07-27 by Walter Harms
  24 .\"     (walter.harms@informatik.uni-oldenburg.de)
  25 .TH LOG1P 3   2007-07-26 "" "Linux Programmer's Manual"
  26 .SH NAME
  27 log1p \-  logarithm of 1 plus argument
  28 .SH SYNOPSIS
  29 .nf
  30 .B #include <math.h>
  31 .sp
  32 .BI "double log1p(double " x );
  33 .br
  34 .BI "float log1pf(float " x );
  35 .br
  36 .BI "long double log1pl(long double " x );
  37 .sp
  38 .fi
  39 Link with \fI\-lm\fP.
  40 .sp
  41 .in -4n
  42 Feature Test Macro Requirements for glibc (see
  43 .BR feature_test_macros (7)):
  44 .in
  45 .sp
  46 .ad l
  47 .BR log1p (),
  48 .BR log1pf (),
  49 .BR log1pl ():
  50 _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 500 || _ISOC99_SOURCE; or
  51 .I cc\ -std=c99
  52 .ad b
  53 .SH DESCRIPTION
  54 .BI log1p( x )
  55 returns a value equivalent to `log (1 + \fIx\fP)'.
  56 It is computed in a way
  57 that is accurate even if the value of \fIx\fP is near zero.
  58 .SH "CONFORMING TO"
  59 BSD, C99.
  60 The
  61 .I float
  62 and
  63 .I "long double"
  64 variants are C99 requirements.
  65 .SH "SEE ALSO"
  66 .BR exp (3),
  67 .BR expm1 (3),
  68 .BR log (3)