man pages section 3: Extended Library Functions

## 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(5).

#### 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(5) for descriptions of the following attributes:

ATTRIBUTE TYPE

ATTRIBUTE VALUE

Interface Stability

See below.

MT-Level

MT-Safe

The scalb() function is Standard. The scalbf() and scalbl() functions are Stable.