LOG2 3CW "09 March 2006" "mathcw-1.00"

Table of contents


NAME

log2f, log2, log2l, log2w, log2q, log2ll, log2df, log2d, log2dl, log2dll - base-2 logarithm function

SYNOPSIS

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

#include <mathcw.h>

extern float log2f (float x);

extern double log2 (double x);

extern long double log2l (long double x);

extern __float80 log2w (__float80 x);

extern __float128 log2q (__float128 x);

extern long_long_double log2ll (long_long_double x);

extern decimal_float log2df (decimal_float x);

extern decimal_double log2d (decimal_double x);

extern decimal_long_double log2dl (decimal_long_double x);

extern decimal_long_long_double log2dll (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 base-2 logarithm of x.

Caution: Avoid use of log2(1 + x) for small-magnitude x; use log21p(x) instead to avoid serious accuracy loss.


RETURN VALUES

Return the base-2 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), log(3CW), log1p(3CW), log21p(3CW), log10(3CW), log101p(3CW), log16(3CW), log161p(3CW).