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log(3) [opendarwin man page]

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 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), 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

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LOG(3)							   BSD Library Functions Manual 						    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. If x is nearly zero, then the common expression log(1 + x) will not be able to produce accurate results, as most (or all) of the information in x will be lost by addition. Instead, use log1p(x) to perform the same computation without undue loss of accuracy. If you find yourself using this function, you are likely to also be interested in the expm1() function. 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. VECTOR OPERATIONS
If you need to apply the log() functions to SIMD vectors or arrays, using the following functions provided by the Accelerate.framework may give significantly better performance: #include <Accelerate/Accelerate.h> vFloat vlogf(vFloat x); vFloat vlog1pf(vFloat x); vFloat vlog10f(vFloat x); void vvlogf(float *y, const float *x, const int *n); void vvlog(double *y, const double *x, const int *n); void vvlog1pf(float *y, const float *x, const int *n); void vvlog1p(double *y, const double *x, const int *n); void vvlog10f(float *y, const float *x, const int *n); void vvlog10(double *y, const double *x, const int *n); void vvlog2f(float *y, const float *x, const int *n); void vvlog2(double *y, const double *x, const int *n); SEE ALSO
exp(3), pow(3), math(3) STANDARDS
The log(), log2(), log10,() and log1p() functions conform to ISO/IEC 9899:2011. 4th Berkeley Distribution August 16, 2012 4th Berkeley Distribution
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