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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
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,
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.,
independently of x.
SEE ALSO
clog(3), cpow(3), fenv(3), ldexp(3), log(3), math(3)
STANDARDS
These functions conform to ISO/IEC 9899:1999 ("ISO C99").
HISTORY
The exp() function appeared in Version 1 AT&T UNIX.
FreeBSD 14.0-RELEASE-p6 April 1, 2020 FreeBSD 14.0-RELEASE-p6