SCALB(3) Library Functions Manual SCALB(3)

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


#include <math.h>

double scalb(double x, double n);

The scalb () function shall compute x * rn, where r is the radix of the machine's floating-point arithmetic. When r is 2, scalb () shall be equivalent to ldexp(3) . The value of r is FLT_RADIX which is defined in <float.h>.

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

Upon successful completion, the scalb () function shall return x * rn.

If x or n is NaN, a NaN shall be returned.

If n is zero, x shall be returned.

If x is ±Inf and n is not -Inf, x shall be returned.

If x is ±0 and n is not +Inf, x shall be returned.

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

If x is ±Inf and n is -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:

If x is zero and n is +Inf, or x is Inf and n is -Inf.

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

The result would overflow. 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.

The scalb () function may fail if:

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.

None.

Applications should use either scalbln(3), scalblnf(3), or scalblnl(3) in preference to this function.

IEEE Std 1003.1-2001 (“POSIX.1”) only defines the behavior for the scalb () function when the n argument is an integer, a NaN, or Inf. The behavior of other values for the n argument 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(3) , fetestexcept(3) , ilogb(3) , ldexp(3) , logb(3) , scalbln(3) , the Base Definitions volume of IEEE Std 1003.1-2001 (“POSIX.1”), xbd_chap04(7), <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 (“ISO C99”) standard, the RETURN VALUE and ERRORS sections are updated to align with the error handling in the ISO/IEC 9899:1999 (“ISO C99”) standard.

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December 6, 2001 posix.fail