Name | Synopsis | Description | Return Values | Errors | Usage | Attributes | See Also
c99 [ flag... ] file... -lm [ library... ] #include <math.h> double scalb(double x, double n);
float scalbf(float x, float n);
long double scalbl(long double x, long double n);
These functions compute x * r^{n}, where r is the radix of the machine's floating point arithmetic. When r is 2, scalb() is equivalent to ldexp(3M). The value of r is FLT_RADIX which is defined in <float.h>.
Upon successful completion, the scalb() function returns x * r^{n}.
If x or n is NaN, a NaN is returned.
If n is 0, x is returned.
If x is ±Inf and n is not -Inf, x is returned.
If x is ±0 and n is not +Inf, x is returned.
If x is ±0 and n is +Inf, a domain error occurs and a NaN is returned.
If x is ±Inf and n is -Inf, a domain error occurs and a NaN is returned.
If the result would cause an overflow, a range error occurs and ±HUGE_VAL (according to the sign of x) is returned.
For exceptional cases, matherr(3M) tabulates the values to be returned by scalb() as specified by SVID3 and XPG3. See standards(5).
These functions will fail if:
If x is 0 and n is +Inf, or x is Inf and n is -Inf.
If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the invalid floating-point exception is raised.
The result would overflow.
If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the overflow floating-point exception is raised.
An application wanting to check for exceptions should call feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an exception has been raised. An application should either examine the return value or check the floating point exception flags to detect exceptions.
See attributes(5) for descriptions of the following attributes:
ATTRIBUTE TYPE |
ATTRIBUTE VALUE |
---|---|
Interface Stability |
See below. |
MT-Level |
MT-Safe |
The scalb() function is Standard. The scalbf() and scalbl() functions are Stable.
feclearexcept(3M), fetestexcept(3M), ilogb(3M), ldexp(3M), logb(3M), math.h(3HEAD), matherr(3M), scalbln(3M), attributes(5), standards(5)
Name | Synopsis | Description | Return Values | Errors | Usage | Attributes | See Also