# expm1(3) [redhat man page]

EXPM1(3) Linux Programmer's Manual EXPM1(3)NAME

expm1, log1p - exponential minus 1, logarithm of 1 plus argumentSYNOPSIS

#include <math.h> double expm1(double x); double log1p(double x);DESCRIPTION

expm1(x) returns a value equivalent to `exp (x) - 1'. It is computed in a way that is accurate even if the value of x is near zero--a case where `exp (x) - 1' would be inaccurate due to subtraction of two numbers that are nearly equal. log1p(x) returns a value equivalent to `log (1 + x)'. It is computed in a way that is accurate even if the value of x is near zero.CONFORMING TO

BSDSEE ALSO

exp(3), log(3)GNU

1995-09-16 EXPM1(3)

## Check Out this Related Man Page

EXPM1(3) Linux Programmer's Manual EXPM1(3)NAME

expm1, expm1f, expm1l - exponential minus 1SYNOPSIS

#include <math.h> double expm1(double x); float expm1f(float x); long double expm1l(long double x); Link withFeature Test Macro Requirements for glibc (see feature_test_macros(7)): expm1(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L; or cc-lm.expm1f(), expm1l(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L; or cc-std=c99-std=c99DESCRIPTION

expm1(x) returns a value equivalent to exp(x) - 1 It is computed in a way that is accurate even if the value of x is near zero--a case where exp(x) - 1 would be inaccurate due to subtrac- tion of two numbers that are nearly equal.RETURN VALUE

On success, these functions return exp(x) - 1. If x is a NaN, a NaN is returned. If x is +0 (-0), +0 (-0) is returned. If x is positive infinity, positive infinity is returned. If x is negative infinity,is returned. If the result overflows, a range error occurs, and the functions return-1,-HUGE_VAL, or-HUGE_VALF, respectively.-HUGE_VALLERRORS

See math_error(7) for information on how to determine whether an error has occurred when calling these functions. The following errors can occur: Range error, overflow errno is set to ERANGE (but see BUGS). An overflow floating-point exception (FE_OVERFLOW) is raised.CONFORMING TO

C99, POSIX.1-2001.BUGS

For some large negative x values (where the function result approaches -1), expm1() raises a bogus underflow floating-point exception. For some large positive x values, expm1() raises a bogus invalid floating-point exception in addition to the expected overflow exception, and returns a NaN instead of positive infinity. Before version 2.11, the glibc implementation did not set errno to ERANGE when a range error occurred.SEE ALSO

exp(3), log(3), log1p(3)COLOPHON

This page is part of release 3.27 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. 2010-09-12 EXPM1(3)