man pages section 3: Extended Library Functions, Volume 2

Updated: Thursday, June 13, 2019

scalb(3M)

Name

scalb, scalbf, scalbl - load exponent of a radix-independent floating-point number

Synopsis

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

double scalb(double x, double n);
float scalbf(float x, float n);
long double scalbl(long double x, long double n);

Description

These functions compute x * rn, where r is the radix of the machine's floating point arithmetic. When r is 2, scalb() is equivalent to ldexp(3M). The value of r is FLT_RADIX which is defined in <float.h>.

Return Values

Upon successful completion, the scalb() function returns x * rn.

If x or n is NaN, a NaN is returned.

If n is 0, x is returned.

If x is ±Inf and n is not −Inf, x is returned.

If x is ±0 and n is not +Inf, x is returned.

If x is ±0 and n is +Inf, a domain error occurs and a NaN is returned.

If x is ±Inf and n is −Inf, a domain error occurs and a NaN is returned.

If the result would cause an overflow, a range error occurs and ±HUGE_VAL (according to the sign of x) is returned.

For exceptional cases, matherr(3M) tabulates the values to be returned by scalb() as specified by SVID3 and XPG3. See standards(7).

Errors

These functions will fail if:

Domain Error

If x is 0 and n is +Inf, or x is Inf and n is −Inf.

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

Range Error

The result would overflow.

If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the overflow 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.

Attributes

See attributes(7) for descriptions of the following attributes:

ATTRIBUTE TYPE
ATTRIBUTE VALUE
Interface Stability
Committed
Availability
system/library/math
MT-Level
MT-Safe
Standard
For scalb(), see standards(7).