
SCALB(P) POSIX Programmer's Manual SCALB(P)
NAME
scalb  load exponent of a radixindependent floatingpoint number
SYNOPSIS
#include <math.h>
double scalb(double x, double n);
DESCRIPTION
The scalb() function shall compute x*r**n, where r is the radix of the machine's floating
point arithmetic. When r is 2, scalb() shall be equivalent to ldexp() . 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
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 nonzero,
an error has occurred.
RETURN VALUE
Upon successful completion, the scalb() function shall return x*r**n.
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 implementationdefined 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 implementationdefined 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.
ERRORS
The scalb() function shall fail if:
Domain Error
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 nonzero, then errno shall be
set to [EDOM]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is nonzero,
then the invalid floatingpoint exception shall be raised.
Range Error
The result would overflow.
If the integer expression (math_errhandling & MATH_ERRNO) is nonzero, then errno shall be
set to [ERANGE]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non
zero, then the overflow floatingpoint exception shall be raised.
The scalb() function may fail if:
Range Error
The result underflows.
If the integer expression (math_errhandling & MATH_ERRNO) is nonzero, then errno shall be
set to [ERANGE]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non
zero, then the underflow floatingpoint exception shall be raised.
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
Applications should use either scalbln(), scalblnf(), or scalblnl() in preference to this
function.
IEEE Std 1003.12001 only defines the behavior for the scalb() function when the n argu
ment 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 nonzero.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
feclearexcept() , fetestexcept() , ilogb() , ldexp() , logb() , scalbln() , the Base Defi
nitions volume of IEEE Std 1003.12001, Section 4.18, Treatment of Error Conditions for
Mathematical Functions, <float.h>, <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) 20012003 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 orig
inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 SCALB(P) 
