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NAME

       scalb - load exponent of a radix-independent floating-point 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 non-zero, 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 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.

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  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.

       Range Error
              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:

       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

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

       IEEE Std 1003.1-2001 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.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       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>

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 .