Manual Pages for UNIX Operating System command usage for man expm1

Mathematical Library Functions                          expm1(3M)



NAME
     expm1, expm1f, expm1l - compute exponential function

SYNOPSIS
     c99 [ flag... ] file... -lm [ library... ]
     #include 

     double expm1(double x);


     float expm1f(float x);


     long double expm1l(long double x);


DESCRIPTION
     These functions compute e^x-1.0.

RETURN VALUES
     Upon successful completion, these functions return e^x-1.0.


     If x is NaN, a NaN is returned.


     If x is +_0, +_0 is returned.


     If x is -Inf, -1 is returned.


     If x is +Inf, x is returned.

ERRORS
     These functions will fail if:

     Range Error    The result overflows.

                    If the integer expression (math_errhandling &
                    MATH_ERREXCEPT)  is  non-zero,  the  overflow
                    floating-point exception is raised.


USAGE
     The value of expm1(x) can 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:




SunOS 5.11          Last change: 12 Jul 2006                    1






Mathematical Library Functions                          expm1(3M)



       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.


     An application wanting to check for exceptions  should  call
     feclearexcept(FE_ALL_EXCEPT) before calling these functions.
     On  return,  if  fetestexcept(FE_INVALID  |  FE_DIVBYZERO  |
     FE_OVERFLOW  |  FE_UNDERFLOW)  is non-zero, an exception has
     been raised. An application should either examine the return
     value  or check the floating point exception flags to detect
     exceptions.

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



     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | Interface Stability         | Committed                   |
    |_____________________________|_____________________________|
    | MT-Level                    | MT-Safe                     |
    |_____________________________|_____________________________|
    | Standard                    | See standards(5).           |
    |_____________________________|_____________________________|


SEE ALSO
     exp(3M),  feclearexcept(3M),  fetestexcept(3M),   ilogb(3M),
     log1p(3M), math.h(3HEAD), attributes(5), standards(5)


















SunOS 5.11          Last change: 12 Jul 2006                    2