LOG(3)

NAME
log, log2, log10, log1p, - logarithm functions

SYNOPSIS
#include <math.h>
double
log(double x);
long double
logl(long double x);
float
logf(float x);
double
log2(double x);
long double
log2l(long double x);
float
log2f(float x);
double
log10(double x);
long double
log10l(long double x);
float
log10f(float x);
double
log1p(double x);
long double
log1pl(long double x);
float
log1pf(float x);

DESCRIPTION
The log() function computes the value of the natural logarithm of argument x.

The log2() function computes the value of the logarithm of argument x to base 2.

The log10() function computes the value of the logarithm of argument x to base 10.

The log1p() function computes the value of log(1+x) accurately even for very small values of x.

SPECIAL VALUES
log(±0) , log2(±0) , and log10(±0) return -infinity and raise the "divide-by-zero" floating-point exception.

log(1) , log2(1) , and log10(1) return +0.

log(x) , log2(x) , and log10(x) return a NaN and raise the "invalid" floating-point exception for x < 0.

log(+infinity) , log2(+infinity) , and log10(+infinity) return +infinity.

log1p(±0) returns ±0.

log1p(-1) returns -infinity and raises the "divide-by-zero" floating-point exception.

log1p(x) returns a NaN and raises the "invalid" floating-point exception for x < -1.

log1p(+infinity) returns +infinity.

SEE ALSO
math(3), exp(3), exp2(3), expm1(3), pow(3)

STANDARDS
The log() , log2() , log10() , and log1p() functions conform to ISO/IEC 9899:1999(E).