`log10f.3p` ( 3 )

функция логарифма по основанию 10 (base 10 logarithm function)

Пролог (Prolog)

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

Имя (Name)

log10, log10f, log10l — base 10 logarithm function

Синопсис (Synopsis)

#include <math.h>

double log10(double x); float log10f(float x); long double log10l(long double x);

Описание (Description)

The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1‐2017 defers to the ISO C standard.

These functions shall compute the base 10 logarithm of their argument x, log10(x).

An application wishing to check for error situations should set errno to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if errno is non-zero or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.

Возвращаемое значение (Return value)

Upon successful completion, these functions shall return the base 10 logarithm of x.

If x is ±0, a pole error shall occur and log10(), log10f(), and log10l() shall 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 shall occur, and either a NaN (if supported), or an implementation-defined value shall be returned.

If x is NaN, a NaN shall be returned.

If x is 1, +0 shall be returned.

If x is +Inf, +Inf shall be returned.

Ошибки (Error)

These functions shall fail if:

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

If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be set to [EDOM]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the invalid floating-point exception shall be raised.

Pole Error The value of x is zero.

If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be set to [ERANGE]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the divide-by-zero floating-point exception shall be raised.

The following sections are informative.

Примеры (Examples)

None.

Использование в приложениях (Application usage)

On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling & MATH_ERREXCEPT) are independent of each other, but at least one of them must be non-zero.

Обоснование (Rationale)

None.

Будущие направления (Future directions)