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SCALBLN(3P) POSIX Programmer's Manual SCALBLN(3P)
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
scalbln, scalblnf, scalblnl, scalbn, scalbnf, scalbnl — compute
exponent using FLT_RADIX
#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);
The functionality described on this reference page is aligned with
the ISO C standard. Any conflict between the requirements described
here and the ISO C standard is unintentional. This volume of
POSIX.1‐2008 defers to the ISO C standard.
These functions shall compute x * FLT_RADIXn efficiently, not
normally by computing FLT_RADIXn 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.
Upon successful completion, these functions shall return
x * FLT_RADIXn.
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 scalbln(), scalblnf(), scalblnl(),
scalbn(), scalbnf(), and scalbnl() shall return 0.0, or (if IEC 60559
Floating-Point is not supported) an implementation-defined value no
greater in magnitude than DBL_MIN, FLT_MIN, LDBL_MIN, DBL_MIN,
FLT_MIN, and LDBL_MIN, respectively.
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.
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.
None.
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.
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.
None.
feclearexcept(3p), fetestexcept(3p)
The Base Definitions volume of POSIX.1‐2008, Section 4.19, Treatment
of Error Conditions for Mathematical Functions, math.h(0p)
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) 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.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the
source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 SCALBLN(3P)
Pages that refer to this page: math.h(0p), ilogb(3p), logb(3p)