Путеводитель по Руководству Linux

  User  |  Syst  |  Libr  |  Device  |  Files  |  Other  |  Admin  |  Head  |



   scalbn    ( 3 )

умножить число с плавающей запятой на целую степень системы счисления (multiply floating-point number by integral power of radix)

Имя (Name)

scalbn, scalbnf, scalbnl, scalbln, scalblnf, scalblnl - multiply floating-point number by integral power of radix


Синопсис (Synopsis)

#include <math.h>

double scalbln(double x, long exp); float scalblnf(float x, long exp); long double scalblnl(long double x, long exp);

double scalbn(double x, int exp); float scalbnf(float x, int exp); long double scalbnl(long double x, int exp);

Link with -lm.

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

scalbln(), scalblnf(), scalblnl(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* Since glibc 2.19: */ _DEFAULT_SOURCE

scalbn(), scalbnf(), scalbnl(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE


Описание (Description)

These functions multiply their first argument x by FLT_RADIX (probably 2) to the power of exp, that is:

x * FLT_RADIX ** exp

The definition of FLT_RADIX can be obtained by including <float.h>.


Возвращаемое значение (Return value)

On success, these functions return x * FLT_RADIX ** exp.

If x is a NaN, a NaN is returned.

If x is positive infinity (negative infinity), positive infinity (negative infinity) is returned.

If x is +0 (-0), +0 (-0) is returned.

If the result overflows, a range error occurs, and the functions return HUGE_VAL, HUGE_VALF, or HUGE_VALL, respectively, with a sign the same as x.

If the result underflows, a range error occurs, and the functions return zero, with a sign the same as x.


Ошибки (Error)

See math_error(7) for information on how to determine whether an error has occurred when calling these functions.

The following errors can occur:

Range error, overflow An overflow floating-point exception (FE_OVERFLOW) is raised.

Range error, underflow errno is set to ERANGE. An underflow floating-point exception (FE_UNDERFLOW) is raised.


Версии (Versions)

These functions first appeared in glibc in version 2.1.


Атрибуты (Attributes)

For an explanation of the terms used in this section, see attributes(7).

┌──────────────────────────────────────┬───────────────┬─────────┐ │Interface Attribute Value │ ├──────────────────────────────────────┼───────────────┼─────────┤ │scalbn(), scalbnf(), scalbnl(), │ Thread safety │ MT-Safe │ │scalbln(), scalblnf(), scalblnl() │ │ │ └──────────────────────────────────────┴───────────────┴─────────┘


Стандарты (Conforming to)

C99, POSIX.1-2001, POSIX.1-2008.


Примечание (Note)

These functions differ from the obsolete functions described in scalb(3) in the type of their second argument. The functions described on this page have a second argument of an integral type, while those in scalb(3) have a second argument of type double.

If FLT_RADIX equals 2 (which is usual), then scalbn() is equivalent to ldexp(3).


Ошибки (баги) (Bugs)

Before glibc 2.20, these functions did not set errno for range errors.


Смотри также (See also)

ldexp(3), scalb(3)