Content-type: text/html Man page of exp

exp

Section: C Library Functions (3)
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NAME

exp, expm1, log, log2, log10, log1p, pow - Exponential, logarithm, and power functions  

LIBRARY

Math Library (libm.a)  

SYNOPSIS

#include <math.h>

double exp (double x); float expf (float x); double expm1 (double x); float expm1f (float x); double log (double x); float logf (float x); double log2 (double x); float log2f (float x); double log10 (double x); float log10f (float x); double log1p (double y); float log1pf (float y); double pow (double x, double y); float powf (float x, float y);  

STANDARDS

Interfaces documented on this reference page conform to industry standards 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() and expf() functions compute the value of the exponential function, defined as e**x, where e is the constant used as a base for natural logarithms.

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

The log() and logf() functions compute the natural (base e) logarithm of x.

The log2() and log2f() functions compute the base 2 logarithm of x.

The log10() and log10f() functions compute the common (base 10) logarithm of x.

The log1p() and log1pf() functions compute log(1+y) accurately, even for tiny y.

The pow() and powf() functions raise a floating-point base x to a floating-point exponent y. The value of pow(x,y) is computed as e**(y ln(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 exceptional arguments:


FunctionExceptional ArgumentRoutine Behavior

exp(), expf()x > ln(max_float)Overflow
exp(), expf()x < ln(min_float)Underflow
expm1(), expm1f()x > ln(max_float)Overflow
expm1(), expm1f()x < ln(min_float)Underflow
log(), logf()x < 0Invalid argument
log(), logf()x = 0Overflow
log2(), log2f()x < 0Invalid argument
log2(), logf2()x = 0Overflow
log10(), log10f()x < 0Invalid argument
log10(), log10f()x = 0Overflow
log1p(), log1pf()1+y < 0Invalid argument
log1p(), log1pf()1+y = 0Overflow
pow(), powf()y ln(x) > ln(max_float)Overflow
pow(), powf()y ln(x) < ln(min_float)Underflow

The following table lists boundary values used by these functions:

ValueDataHexadecimal ValueDecimal Value
NameType

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

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Index

NAME
LIBRARY
SYNOPSIS
STANDARDS
DESCRIPTION

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Time: 02:41:14 GMT, October 02, 2010