LOG 3CW "09 March 2006" "mathcw-1.00"

Table of contents


NAME

logf, log, logl, logw, logq, logll, logdf, logd, logdl, logdll - natural (base-e) logarithm function

SYNOPSIS

cc [ flags ] -I/usr/local/include file(s) -L/usr/local/lib -lmcw [ ... ]

#include <mathcw.h>

extern float logf (float x);

extern double log (double x);

extern long double logl (long double x);

extern __float80 logw (__float80 x);

extern __float128 logq (__float128 x);

extern long_long_double logll (long_long_double x);

extern decimal_float logdf (decimal_float x);

extern decimal_double logd (decimal_double x);

extern decimal_long_double logdl (decimal_long_double x);

extern decimal_long_long_double logdll (decimal_long_long_double x);

NB: Functions with prototypes containing underscores in type names may be available only with certain extended compilers.


DESCRIPTION

Compute the natural (base-e, where e = 2.818281828...) logarithm of x.

Caution: Avoid use of log(1 + x) for small-magnitude x; use log1p(x) instead to avoid serious accuracy loss.


RETURN VALUES

Return the natural logarithm of the argument.

ERRORS

If the argument is negative or zero, set errno to EDOM and return a quiet NaN. If the argument is a NaN, set errno to EDOM and return the argument. If the argument is +Infinity, set errno to ERANGE and return the argument.

SEE ALSO

exp(3CW), expm1(3CW), exp2(3CW), exp2m1(3CW), exp10(3CW), exp10m1(3CW), exp16(3CW), exp16m1(3CW), log1p(3CW), log2(3CW), log21p(3CW), log10(3CW), log101p(3CW), log16(3CW), log161p(3CW).