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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 argu-ment argument 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 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). 4th Berkeley Distribution July 2, 2003 4th Berkeley Distribution |