умножить число с плавающей запятой на целую степень 2 (multiply floating-point number by integral power of 2)
Имя (Name)
ldexp, ldexpf, ldexpl - multiply floating-point number by
integral power of 2
Синопсис (Synopsis)
#include <math.h>
double ldexp(double x, int exp);
float ldexpf(float x, int exp);
long double ldexpl(long double x, int exp);
Link with -lm.
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
ldexpf(), ldexpl():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
Описание (Description)
These functions return the result of multiplying the floating-
point number x by 2 raised to the power exp.
Возвращаемое значение (Return value)
On success, these functions return x * (2^exp).
If exp is zero, then x is returned.
If x is a NaN, a NaN is returned.
If x is positive infinity (negative infinity), positive infinity
(negative infinity) is returned.
If the result underflows, a range error occurs, and zero 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.
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
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 │
├──────────────────────────────────────┼───────────────┼─────────┤
│ldexp(), ldexpf(), ldexpl() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘
Стандарты (Conforming to)
C99, POSIX.1-2001, POSIX.1-2008.
The variant returning double also conforms to SVr4, 4.3BSD, C89.
Смотри также (See also)
frexp(3), modf(3), scalbln(3)
