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EXP(3)		       FreeBSD Library Functions Manual			EXP(3)

NAME
     exp, expf,	expl, exp2, exp2f, exp2l, expm1, expm1f, expm1l, pow, powf,
     powl -- 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);

     long double
     powl(long double x, long double 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(),	powf(),	and the	powl() 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), powf(x,
     y), and powl(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,	infin-
     ity, 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 return-
     ing 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 any-
	     way since that expression's meaning and, if invalid, its conse-
	     quences 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 any-
	     thing 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.

BUGS
     To	conform	with newer C/C++ standards, a stub implementation for powl was
     committed to the math library, where powl is mapped to pow.  Thus,	the
     numerical accuracy	is at most that	of the 53-bit double precision imple-
     mentation.

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

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

FreeBSD	11.2		       December	8, 2017			  FreeBSD 11.2

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | ERROR (due to Roundoff etc.) | RETURN VALUES | NOTES | BUGS | SEE ALSO | STANDARDS

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