expm1f(3) [netbsd man page]

EXP(3)							   BSD Library Functions Manual 						    EXP(3)

NAME

     exp, expf, exp2, exp2f, expm1, expm1f, -- exponential functions

LIBRARY

     Math Library (libm, -lm)

SYNOPSIS

     #include <math.h>

     double
     exp(double x);

     float
     expf(float x);

     double
     exp2(double x);

     float
     exp2f(float x);

     double
     expm1(double x);

     float
     expm1f(float x);

DESCRIPTION

     The exp() and the expf() functions compute the base e exponential value of the given argument x.

     The exp2(), and exp2f() functions compute the base 2 exponential of the given argument x.

     The expm1() and the expm1f() functions computes the value exp(x)-1 accurately even for tiny argument x.

RETURN VALUES

     These functions will return the appropriate computation unless an error occurs or an argument is out of range.  The functions exp() and
     expm1() detect if the computed value will overflow, set the global variable errno to ERANGE and cause a reserved operand fault on a VAX.

SEE ALSO

     math(3)

STANDARDS

     The exp() functions conform to ANSI X3.159-1989 (``ANSI C89'').  The exp2(), exp2f(), expf(), expm1(), and expm1f() functions conform to
     ISO/IEC 9899:1999 (``ISO C99'').

HISTORY

     The exp() functions appeared in Version 6 AT&T UNIX.  The expm1() function appeared in 4.3BSD.

BSD
								September 13, 2011							       BSD

EXP(3)							   BSD Library Functions Manual 						    EXP(3)

NAME

     exp, expf, expl, exp2, exp2f, exp2l, expm1, expm1f, expm1l, pow, powf -- exponential and power functions

LIBRARY

     Math Library (libm, -lm)

SYNOPSIS

     #include <math.h>

     double
     exp(double x);

     float
     expf(float x);

     long double
     expl(long double x);

     double
     exp2(double x);

     float
     exp2f(float x);

     long double
     exp2l(long double x);

     double
     expm1(double x);

     float
     expm1f(float x);

     long double
     expm1l(long double x);

     double
     pow(double x, double y);

     float
     powf(float x, float y);

DESCRIPTION

     The exp(), expf(), and expl() functions compute the base e exponential value of the given argument x.

     The exp2(), exp2f(), and exp2l() functions compute the base 2 exponential of the given argument x.

     The expm1(), expm1f(), and the expm1l() functions compute the value exp(x)-1 accurately even for tiny argument x.

     The pow() and the powf() functions compute the value of x to the exponent y.

ERROR (due to Roundoff etc.)
     The values of exp(0), expm1(0), exp2(integer), and pow(integer, integer) are exact provided that they are representable.  Otherwise the error
     in these functions is generally below one ulp.

RETURN VALUES

     These functions will return the appropriate computation unless an error occurs or an argument is out of range.  The functions pow(x, y) and
     powf(x, y) raise an invalid exception and return an NaN if x < 0 and y is not an integer.

NOTES

     The function pow(x, 0) returns x**0 = 1 for all x including x = 0, infinity, and NaN .  Previous implementations of pow may have defined x**0
     to be undefined in some or all of these cases.  Here are reasons for returning x**0 = 1 always:

     1.      Any program that already tests whether x is zero (or infinite or NaN) before computing x**0 cannot care whether 0**0 = 1 or not.  Any
	     program that depends upon 0**0 to be invalid is dubious anyway since that expression's meaning and, if invalid, its consequences vary
	     from one computer system to another.

     2.      Some Algebra texts (e.g. Sigler's) define x**0 = 1 for all x, including x = 0.  This is compatible with the convention that accepts
	     a[0] as the value of polynomial

		   p(x) = a[0]*x**0 + a[1]*x**1 + a[2]*x**2 +...+ a[n]*x**n

	     at x = 0 rather than reject a[0]*0**0 as invalid.

     3.      Analysts will accept 0**0 = 1 despite that x**y can approach anything or nothing as x and y approach 0 independently.  The reason for
	     setting 0**0 = 1 anyway is this:

		   If x(z) and y(z) are any functions analytic (expandable in power series) in z around z = 0, and if there x(0) = y(0) = 0, then
		   x(z)**y(z) -> 1 as z -> 0.

     4.      If 0**0 = 1, then infinity**0 = 1/0**0 = 1 too; and then NaN**0 = 1 too because x**0 = 1 for all finite and infinite x, i.e., inde-
	     pendently of x.

SEE ALSO

     fenv(3), ldexp(3), log(3), math(3)

STANDARDS

     These functions conform to ISO/IEC 9899:1999 (``ISO C99'').

BSD
								   June 3, 2013 							       BSD