1LOG1P(3)                   Linux Programmer's Manual                  LOG1P(3)
2
3
4

NAME

6       log1p, log1pf, log1pl -  logarithm of 1 plus argument
7

SYNOPSIS

9       #include <math.h>
10
11       double log1p(double x);
12       float log1pf(float x);
13       long double log1pl(long double x);
14
15       Link with -lm.
16
17   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
18
19       log1p(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 ||
20       _ISOC99_SOURCE; or cc -std=c99
21       log1pf(), log1pl(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600
22       || _ISOC99_SOURCE; or cc -std=c99
23

DESCRIPTION

25       log1p(x) returns a value equivalent to
26
27           log (1 + x)
28
29       It is computed in a way that is accurate even if the value of x is near
30       zero.
31

RETURN VALUE

33       On success, these functions return the natural logarithm of (1 + x).
34
35       If x is a NaN, a NaN is returned.
36
37       If x is positive infinity, positive infinity is returned.
38
39       If x is -1, a pole error occurs, and the  functions  return  -HUGE_VAL,
40       -HUGE_VALF, or -HUGE_VALL, respectively.
41
42       If  x  is  less  than  -1 (including negative infinity), a domain error
43       occurs, and a NaN (not a number) is returned.
44

ERRORS

46       See math_error(7) for information on how to determine whether an  error
47       has occurred when calling these functions.
48
49       The following errors can occur:
50
51       Domain error: x is less than -1
52              An invalid floating-point exception (FE_INVALID) is raised.
53
54       Pole error: x is -1
55              A  divide-by-zero  floating-point  exception  (FE_DIVBYZERO)  is
56              raised.
57
58       These functions do not set errno.
59

CONFORMING TO

61       C99, POSIX.1-2001.
62

SEE ALSO

64       exp(3), expm1(3), log(3)
65

COLOPHON

67       This page is part of release 3.25 of the Linux  man-pages  project.   A
68       description  of  the project, and information about reporting bugs, can
69       be found at http://www.kernel.org/doc/man-pages/.
70
71
72
73                                  2008-08-05                          LOG1P(3)
Impressum