Tribblix: manual page: log10.3m

LOG10(3M) Mathematical Library Functions LOG10(3M)

NAME

log10, log10f, log10l - base 10 logarithm function

SYNOPSIS

c99 [ flag... ] file... -lm [ library... ]
#include <math.h>

double log10(double x);

float log10f(float x);

long double log10l(long double x);

DESCRIPTION

These functions compute the base 10 logarithm of x, log(10)(x).

RETURN VALUES

Upon successful completion, log10() returns the base 10 logarithm of
x.

If x is +-0, a pole error occurs and log10(), log10f(), and log10l()
return -HUGE_VAL, -HUGE_VALF, and -HUGE_VALL, respectively.

For finite values of x that are less than 0, or if x is -Inf, a
domain error occurs and a NaN is returned.

If x is NaN, a NaN is returned.

If x is 1, +0 is returned.

If x is +Inf, x is returned.

For exceptional cases, matherr(3M) tabulates the values to be
returned by log10() as specified by SVID3 and XPG3.

ERRORS

These functions will fail if:

Domain Error
The finite value of x is negative, or x is -Inf.

If the integer expression (math_errhandling &
MATH_ERREXCEPT) is non-zero, the invalid floating-
point exception is raised.

The log10() function sets errno to EDOM if the value
of x is negative.

Pole Error
The value of x is 0.

If the integer expression (math_errhandling &
MATH_ERREXCEPT) is non-zero, the divide-by-zero
floating-point exception is raised.

USAGE

An application wanting to check for exceptions should call
feclearexcept(FE_ALL_EXCEPT) before calling these functions. On
return, if fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW |
FE_UNDERFLOW) is non-zero, an exception has been raised. An
application should either examine the return value or check the
floating point exception flags to detect exceptions.

An application can also set errno to 0 before calling log10(). On
return, if errno is non-zero, an error has occurred. The log10f() and
log10l() functions do not set errno.

ATTRIBUTES