# scalbn (3p) - Linux Manuals

## scalbn: compute exponent

## PROLOG

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.## NAME

scalbln, scalblnf, scalblnl, scalbn, scalbnf, scalbnl - compute exponent using FLT_RADIX

## SYNOPSIS

**#include <math.h>
**

**
double scalbln(double** *x***, long** *n***);
float scalblnf(float**

*x*

**, long**

*n*

**);**

long double scalblnl(long double

long double scalblnl(long double

*x*

**, long**

*n*

**);**

double scalbn(double

double scalbn(double

*x*

**, int**

*n*

**);**

float scalbnf(float

float scalbnf(float

*x*

**, int**

*n*

**);**

long double scalbnl(long double

long double scalbnl(long double

*x*

**, int**

*n*

**);**

## DESCRIPTION

These functions shall compute *x* ***n* efficiently,
not normally by
computing FLT_RADIX***n* explicitly.

An application wishing to check for error situations should set *errno*
to zero and call
*feclearexcept*(FE_ALL_EXCEPT) before calling these functions.
On return, if *errno* is non-zero or
*fetestexcept*(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW)
is non-zero, an error has occurred.

## RETURN VALUE

Upon successful completion, these functions shall return *x* ***n*.

If the result would cause overflow, a range error shall occur and
these functions shall return ±HUGE_VAL,
±HUGE_VALF, and ±HUGE_VALL (according to the sign of *x*)
as appropriate for the return type of the
function.

If the correct value would cause underflow, and is not representable, a range error may occur, and either 0.0 (if supported), or an implementation-defined value shall be returned.

If
*x* is NaN, a NaN shall be returned.

If *x* is ±0 or ±Inf, *x* shall be returned.

If *n* is 0, *x* shall be returned.

If the correct value would cause underflow, and is representable, a range error may occur and the correct value shall be returned.

## ERRORS

These functions shall fail if:

- Range Error
- The result overflows.

If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
then *errno* shall be set to [ERANGE]. If the
integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero,
then the overflow floating-point exception shall be
raised.

These functions may fail if:

- Range Error
- The result underflows.

If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
then *errno* shall be set to [ERANGE]. If the
integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero,
then the underflow floating-point exception shall be
raised.

*The following sections are informative.*

## EXAMPLES

## APPLICATION USAGE

On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling & MATH_ERREXCEPT) are independent of each other, but at least one of them must be non-zero.

## RATIONALE

These functions are named so as to avoid conflicting with the historical
definition of the *scalb*() function from the Single UNIX Specification.
The difference is that the *scalb*() function has a second argument
of **double** instead of **int**. The *scalb*() function is
not part of the ISO C standard. The three functions whose second
type
is **long** are provided because the factor required to scale from
the smallest positive floating-point value to the largest
finite one, on many implementations, is too large to represent in
the minimum-width **int** format.

## FUTURE DIRECTIONS

## COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

## SEE ALSO

*feclearexcept*(), *fetestexcept*(), *scalb*(), the
Base Definitions volume of IEEE Std 1003.1-2001, Section 4.18, Treatment
of Error Conditions for Mathematical Functions, *<math.h>*