SCALBLN(P) SCALBLN(P)
NAME
scalbln, scalblnf, scalblnl, scalbn, scalbnf, scalbnl - compute exponent using FLT_RADIX
SYNOPSIS
#include <math.h>
double scalbln(double x, long n);
float scalblnf(float x, long n);
long double scalblnl(long double x, long n);
double scalbn(double x, int n);
float scalbnf(float x, int n);
long double scalbnl(long double x, int n);
DESCRIPTION
These functions shall compute x * FLT_RADIX**n efficiently, not normally by computing
FLT_RADIX**n explicitly.
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, these functions shall return x * FLT_RADIX**n.
If the result would cause overflow, a range error shall occur and these functions shall
return ?HUGE_VAL, ?HUGE_VALF, and ?HUGE_VALL (according to the sign of x) as appropriate
for the return type of the function.
If the correct value would cause underflow, and is not representable, a range error may
occur, and either 0.0 (if supported), or an implementation-defined value shall be
returned.
If x is NaN, a NaN shall be returned.
If x is ?0 or ?Inf, x shall be returned.
If n is 0, 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.
ERRORS
These functions shall fail if:
Range Error
The result overflows.
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.
These functions 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
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
These functions are named so as to avoid conflicting with the historical definition of the
scalb() function from the Single UNIX Specification. The difference is that the scalb()
function has a second argument of double instead of int. The scalb() function is not part
of the ISO C standard. The three functions whose second type is long are provided because
the factor required to scale from the smallest positive floating-point value to the
largest finite one, on many implementations, is too large to represent in the minimum-
width int format.
FUTURE DIRECTIONS
None.
SEE ALSO
feclearexcept() , fetestexcept() , scalb() , the Base Definitions volume of
IEEE Std 1003.1-2001, Section 4.18, Treatment of Error Conditions for Mathematical Func-
tions, <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 orig-
inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .
POSIX 2003 SCALBLN(P)
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