LOG(3) NetBSD Library Functions Manual LOG(3)NAMElog,logf,log10,log10f,log1p,log1pf log2,log2f, -- logarithm func- tionsLIBRARYMath Library (libm, -lm)SYNOPSIS#include <math.h>doublelog(double x);floatlogf(float x);doublelog10(double x);floatlog10f(float x);doublelog1p(double x);floatlog1pf(float x);doublelog2(double x);floatlog2f(float x);DESCRIPTIONThe following functions compute logarithms:·Thelog() andlogf() functions return the natural logarithm.·Thelog10() andlog10f() functions return the base 10 logarithm.·Thelog1p() andlog1pf() functions return the natural logarithm of (1.0 +x) accurately even for very small values ofx.·Thelog2() andlog2f() functions return the base 2 logarithm.RETURN VALUESUpon successful completion, the functions return the logarithm ofxas descibed above. Otherwise the following may occur: 1. IfxisNaN, all functions returnNaN. 2. Ifxis positive infinity, all functions returnx. Ifxis negative infinity, all functions returnNaN. 3. Ifxis +0.0 or -0.0, thelog(),log10(), andlog2() families return either -HUGE_VAL, -HUGE_VALF, or -HUGE_VALL, whereas thelog1p() family returnsx. 4. Ifxis +1.0, thelog(),log10(), andlog2() families return +0.0. Ifxis -1.0, thelog1p() family returns -HUGE_VAL, -HUGE_VALF, or -HUGE_VALL. In addition, on a VAX,errnois set to EDOM and the reserved operand is returned bylog() unlessx> 0, bylog1p() unlessx> -1.SEE ALSOexp(3), ilogb(3), math(3)STANDARDSThe described functions conform to ISO/IEC 9899:1999 (``ISO C99'').HISTORYThe history of the logarithm functions dates back to Version 6 AT&T UNIX. NetBSD 7.1.2 September 13, 2011 NetBSD 7.1.2

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