IEEE Std 1003.1, 2004 Edition

Copyright © 2001-2004 The IEEE and The Open Group, All Rights reserved.

scalb - load exponent of a radix-independent floating-point number

^{[OB XSI]}#include <math.h>

double scalb(doublex, doublen);

The

scalb() function shall computex*r, where^{n}ris the radix of the machine's floating-point arithmetic. Whenris 2,scalb() shall be equivalent toldexp(). The value ofris FLT_RADIX which is defined in<float.h>.An application wishing to check for error situations should set

errnoto zero and callfeclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, iferrnois non-zero orfetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.

Upon successful completion, the

scalb() function shall returnx*r.^{n}If

xornis NaN, a NaN shall be returned.If

nis zero,xshall be returned.If

xis ±Inf andnis not -Inf,xshall be returned.If

xis ±0 andnis not +Inf,xshall be returned.If

xis ±0 andnis +Inf, a domain error shall occur, and either a NaN (if supported), or an implementation-defined value shall be returned.If

xis ±Inf andnis -Inf, a domain error shall occur, and either a NaN (if supported), or an implementation-defined value shall be returned.If the result would cause an overflow, a range error shall occur and ±HUGE_VAL (according to the sign of

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.

If the correct value would cause underflow, and is not representable, a range error may occur, and 0.0 shall be returned.

The

scalb() function shall fail if:

- Domain Error
- If
xis zero andnis +Inf, orxis Inf andnis -Inf.If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then

errnoshall be set to [EDOM]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the invalid floating-point exception shall be raised.- Range Error
- The result would overflow.
If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then

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

scalb() function may fail if:

- Range Error
- The result underflows.
If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then

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

None.

Applications should use either

scalbln(),scalblnf(), orscalblnl() in preference to this function.IEEE Std 1003.1-2001 only defines the behavior for the

scalb() function when thenargument is an integer, a NaN, or Inf. The behavior of other values for thenargument is unspecified.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.

None.

None.

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

First released in Issue 4, Version 2.

Moved from X/OPEN UNIX extension to BASE.

The DESCRIPTION is updated to indicate how an application should check for an error. This text was previously published in the APPLICATION USAGE section.

This function is marked obsolescent.

Although this function is not part of the ISO/IEC 9899:1999 standard, the RETURN VALUE and ERRORS sections are updated to align with the error handling in the ISO/IEC 9899:1999 standard.

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