expm1(3M)

NAME

     expm1 - computes exponential functions

SYNOPSIS

     cc [ flag ... ] file ... -lm [ library ... ]
     #include <math.h>

     double expm1(double x);

DESCRIPTION

     The expm1() function computes e**x-1.0.

RETURN VALUES

     If x is NaN, then the function returns NaN.

     If x is positive infinity, expm1() returns  positive  infin-
     ity.

     If x is negative infinity, expm1() returns -1.0.

     If the value overflows, expm1() returns HUGE_VAL.

ERRORS

     No errors will occur.

USAGE

     The value of expm1(x) may be more accurate  than  exp(x)-1.0
     for small values of x.

     The expm1() and log1p(3M) functions are useful for financial
     calculations of ((1+x)**n-1)/x, namely:

     expm1(n * log1p(x))/x

     when x is very small (for example, when performing  calcula-
     tions  with  a  small daily interest rate).  These functions
     also simplify writing accurate inverse hyperbolic functions.

ATTRIBUTES

     See attributes(5) for descriptions of the  following  attri-
     butes:

     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | MT-Level                    | MT-Safe                     |
    |_____________________________|_____________________________|

SEE ALSO

     exp(3M), ilogb(3M), log1p(3M), attributes(5)