scalb(3) Library Functions Manual scalb(3)
NAME
scalb, scalbf, scalbl - multiply floating-point number by integral
power of radix (OBSOLETE)
LIBRARY
Math library (libm, -lm)
SYNOPSIS
#include <math.h>
[[deprecated]] double scalb(double x, double exp);
[[deprecated]] float scalbf(float x, float exp);
[[deprecated]] long double scalbl(long double x, long double exp);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
scalb():
_XOPEN_SOURCE >= 500
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
scalbf(), scalbl():
_XOPEN_SOURCE >= 600
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
DESCRIPTION
These functions multiply their first argument x by FLT_RADIX (probably
2) to the power of exp, that is:
x * FLT_RADIX ** exp
The definition of FLT_RADIX can be obtained by including <float.h>.
RETURN VALUE
On success, these functions return x * FLT_RADIX ** exp.
If x or exp is a NaN, a NaN is returned.
If x is positive infinity (negative infinity), and exp is not negative
infinity, positive infinity (negative infinity) is returned.
If x is +0 (-0), and exp is not positive infinity, +0 (-0) is returned.
If x is zero, and exp is positive infinity, a domain error occurs, and
a NaN is returned.
If x is an infinity, and exp is negative infinity, a domain error oc-
curs, and a NaN is returned.
If the result overflows, a range error occurs, and the functions return
HUGE_VAL, HUGE_VALF, or HUGE_VALL, respectively, with a sign the same
as x.
If the result underflows, a range error occurs, and the functions re-
turn zero, with a sign the same as x.
ERRORS
See math_error(7) for information on how to determine whether an error
has occurred when calling these functions.
The following errors can occur:
Domain error: x is 0, and exp is positive infinity, or x is positive
infinity and exp is negative infinity and the other argument is not a
NaN
errno is set to EDOM. An invalid floating-point exception
(FE_INVALID) is raised.
Range error, overflow
errno is set to ERANGE. An overflow floating-point exception
(FE_OVERFLOW) is raised.
Range error, underflow
errno is set to ERANGE. An underflow floating-point exception
(FE_UNDERFLOW) is raised.
ATTRIBUTES
For an explanation of the terms used in this section, see at-
tributes(7).
┌────────────────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├────────────────────────────────────────────┼───────────────┼─────────┤
│scalb(), scalbf(), scalbl() │ Thread safety │ MT-Safe │
└────────────────────────────────────────────┴───────────────┴─────────┘
STANDARDS
scalb() is specified in POSIX.1-2001, but marked obsolescent.
POSIX.1-2008 removes the specification of scalb(), recommending the use
of scalbln(3), scalblnf(3), or scalblnl(3) instead. The scalb() func-
tion is from 4.3BSD.
scalbf() and scalbl() are unstandardized; scalbf() is nevertheless
present on several other systems
BUGS
Before glibc 2.20, these functions did not set errno for domain and
range errors.
SEE ALSO
ldexp(3), scalbln(3)
Linux man-pages 6.03 2023-02-05 scalb(3)
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