expm1(3M)						  Mathematical Library Functions						 expm1(3M)

NAME

       expm1, expm1f, expm1l - compute exponential function

SYNOPSIS

       c99 [ flag... ] file... -lm [ library... ]
       #include <math.h>

       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:

	 expm1(n * log1p(x))/x

       when  x	is very small (for example, when performing calculations 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 attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |MT-Safe			   |
       +-----------------------------+-----------------------------+

SEE ALSO

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

SunOS 5.11							    12 Jul 2006 							 expm1(3M)