Originální popis anglicky:
scalb - load exponent of a radix-independent floating-point number
Návod, kniha: POSIX Programmer's Manual
#include <math.h>
double scalb(double
x, double
n );
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.
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.
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.
None.
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.
None.
None.
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>
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
.
