умножить число с плавающей запятой на целую степень системы счисления (УСТАРЕЛО) (multiply floating-point number by integral power of radix (OBSOLETE))
Имя (Name)
scalb, scalbf, scalbl - multiply floating-point number by
integral power of radix (OBSOLETE)
Синопсис (Synopsis)
#include <math.h>
double scalb(double x, double exp);
float scalbf(float x, float exp);
long double scalbl(long double x, long double exp);
Link with -lm.
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
scalb():
_XOPEN_SOURCE >= 500
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
scalbf(), scalbl():
_XOPEN_SOURCE >= 600
|| /* 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 or exp is a NaN, a NaN is returned.
If x is positive infinity (negative infinity), and exp is not
negative infinity, positive infinity (negative infinity) is
returned.
If x is +0 (-0), and exp is not positive infinity, +0 (-0) is
returned.
If x is zero, and exp is positive infinity, a domain error
occurs, and a NaN is returned.
If x is an infinity, and exp is negative infinity, a domain error
occurs, and a NaN 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:
Domain error: x is 0, and exp is positive infinity, or x is
positive infinity and exp is negative infinity and the other
argument is not a NaN
errno is set to EDOM. An invalid floating-point exception
(FE_INVALID) is raised.
Range error, overflow
errno is set to ERANGE. 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.
Атрибуты (Attributes)
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├──────────────────────────────────────┼───────────────┼─────────┤
│scalb(), scalbf(), scalbl() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘
Стандарты (Conforming to)
scalb() is specified in POSIX.1-2001, but marked obsolescent.
POSIX.1-2008 removes the specification of scalb(), recommending
the use of scalbln(3), scalblnf(3), or scalblnl(3) instead. The
scalb() function is from 4.3BSD.
scalbf() and scalbl() are unstandardized; scalbf() is
nevertheless present on several other systems
Ошибки (баги) (Bugs)
Before glibc 2.20, these functions did not set errno for domain
and range errors.
Смотри также (See also)
ldexp(3), scalbln(3)
