# scalb - Man Page

multiply floating-point number by integral power of radix (OBSOLETE)

## 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```

## 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>.

## 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.

## Errors

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.

## Attributes

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

InterfaceAttributeValue
scalb(), scalbf(), scalbl()Thread safetyMT-Safe

## 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

## Bugs

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