exp(3)exp(3)NAME
exp, expm1, log, log2, log10, log1p, pow - Exponential, logarithm, and
power functions
SYNOPSIS
#include <math.h>
double exp(
double x ); float expf(
float x ); long double expl(
long double x ); double expm1(
double x ); float expm1f(
float x ); long double expm1l(
long double x ); double log(
double x ); float logf(
float x ); long double logl(
long double x ); double log2(
double x ); float log2f(
float x ); long double log2l(
long double x ); double log10(
double x ); float log10f(
float x ); long double log10l(
long double x ); double log1p(
double y ); float log1pf(
float y ); long double log1pl(
long double y ); double pow(
double x,
double y ); float powf(
float x,
float y ); long double powl(
long double x,
long double y );
LIBRARY
Math Library (libm)
STANDARDS
Interfaces documented on this reference page conform to industry stan‐
dards as follows:
exp(): XPG4
expm1(): XPG4-UNIX
log(): XPG4
log10(): XPG4
log1p(): XPG4-UNIX
pow(): XPG4
Refer to the standards(5) reference page for more information about
industry standards and associated tags.
DESCRIPTION
The exp(), expf(), and expl() functions compute the value of the expo‐
nential function, defined as e**x, where e is the constant used as a
base for natural logarithms.
The expm1(), expm1f(), and expm1l() functions compute exp(x) - 1 accu‐
rately, even for tiny x.
The log(), logf(), and logl() functions compute the natural (base e)
logarithm of x.
The log2(), log2f(), and log2l() functions compute the base 2 logarithm
of x.
The log10(), log10f(), and log10l() functions compute the common (base
10) logarithm of x.
The log1p(), log1pf(), and log1pl() functions compute log(1+y) accu‐
rately, even for tiny y.
The pow(), powf(), and powl() functions raise a floating-point base x
to a floating-point exponent y. The value of pow(x,y) is computed as
e**(yln(x)) for positive x. If x is 0 or negative, see your language
reference manual.
Passing a NaN input value to pow() produces a NaN result for y not
equal to 0. For pow(NaN,0), see your language reference manual.
The following table describes function behavior in response to excep‐
tional arguments:
────────────────────────────────────────────────────────────────────────────
Function Exceptional Argument Routine Behav‐
ior
────────────────────────────────────────────────────────────────────────────
exp(), expf(), expl() x > ln(max_float) Overflow
exp(), expf(), expl() x < ln(min_float) Underflow
expm1(), expm1f(), expm1l () x > ln(max_float) Overflow
expm1(), expm1f(), expm1l () x < ln(min_float) Underflow
log(), logf(), logl() x < 0 Invalid argu‐
ment
log(), logf(), logl() x = 0 Overflow
log2(), log2f(), log2l () x < 0 Invalid argu‐
ment
log2(), logf2(), log2l () x = 0 Overflow
log10(), log10f(), log10l () x < 0 Invalid argu‐
ment
log10(), log10f(), log10l () x = 0 Overflow
log1p(), log1pf(), log1pl () 1+y < 0 Invalid argu‐
ment
log1p(), log1pf(), log1pl () 1+y = 0 Overflow
pow(), powf(), powl() y ln(x) > ln(max_float) Overflow
pow(), powf(), powl() y ln(x) < ln(min_float) Underflow
────────────────────────────────────────────────────────────────────────────
The following table lists boundary values used by these functions:
───────────────────────────────────────────────────────────────────
Value Name Data Type Hexadecimal Value Decimal Value
───────────────────────────────────────────────────────────────────
ln(max_float) S_FLOAT 42B17218 88.7228391
T_FLOAT 40862E42FEFA39EF 709.7827128933840
ln(min_float) S_FLOAT C2CE8ED0 -103.2789
T_FLOAT C0874385446D71C3 -744.4400719213813
───────────────────────────────────────────────────────────────────
exp(3)
