SCALBLN(3P) | POSIX Programmer's Manual | SCALBLN(3P) |

# 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>**

*x*

**, long**

*n*

**);**

*x*

**, long**

*n*

**);**

*x*

**, long**

*n*

**);**

*x*

**, int**

*n*

**);**

*x*

**, int**

*n*

**);**

*x*

**, int**

*n*

**);**

# DESCRIPTION

These functions shall compute*x** FLT_RADIX

***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** FLT_RADIX

***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

None.# 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

None.# 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>*

# 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 .2003 | IEEE/The Open Group |