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

NAME
       expm1, expm1f, expm1l - exponential minus 1

SYNOPSIS
       #include 

       double expm1(double x);
       float expm1f(float x);
       long double expm1l(long double x);

       Link with -lm.

   Feature Test Macro Requirements for glibc (see featuretestmacros(7)):

       expm1():
           BSDSOURCE || SVIDSOURCE || XOPENSOURCE >= 500 ||
           XOPENSOURCE && XOPENSOURCEEXTENDED || ISOC99SOURCE ||
           POSIXCSOURCE >= 200112L;
           or cc -std=c99
       expm1f(), expm1l():
           BSDSOURCE || SVIDSOURCE || XOPENSOURCE >= 600 ||
           ISOC99SOURCE || POSIXCSOURCE >= 200112L;
           or cc -std=c99

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.

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, -1 is returned.

       If the result overflows, a range error occurs, and the functions return
       -HUGEVAL, -HUGEVALF, or -HUGEVALL, respectively.

ERRORS
       See  matherror(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 (FEOVERFLOW) is raised.


ATTRIBUTES
       For   an   explanation   of   the  terms  used  in  this  section,  see
       attributes(7).

       ┌────────────────────────────┬───────────────┬─────────┐
       │Interface                   │ Attribute     │ Value   │
       ├────────────────────────────┼───────────────┼─────────┤
       │expm1(), expm1f(), expm1l() │ Thread safety │ MT-Safe │
       └────────────────────────────┴───────────────┴─────────┘
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 float‐
       ing-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 3.53 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)