LOG(3) BSD Library Functions Manual LOG(3)NAME
log, log2, log10, log1p, — logarithm functions
SYNOPSIS
#include <math.h>
double
log(double x);
double
log2(double x);
double
log10(double x);
double
log1p(double x);
DESCRIPTION
The log() function computes the value of the natural logarithm of argu‐
ment 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 ALSOmath(3), exp(3), exp2(3), expm1(3), pow(3), infnan(3)STANDARDS
The log() , log2() , log10() , and log1p() functions conform to ISO/IEC
9899:1999(E).
4th Berkeley Distribution July 2, 2003 4th Berkeley Distribution