scalbn(3)

NAME#

scalbn, scalbnf, scalbnl, scalbln, scalblnf, scalblnl - multiply floating-point number by integral power of radix

LIBRARY#

Math library (libm, -lm)

SYNOPSIS#

#include <math.h>

double scalbln(double \nx\n, long \nexp\n);\n
\nfloat scalblnf(float \nx\n, long \nexp\n);\n
\nlong double scalblnl(long double \nx\n, long \nexp\n);

double scalbn(double \nx\n, int \nexp\n);\n
\nfloat scalbnf(float \nx\n, int \nexp\n);\n
\nlong double scalbnl(long double \nx\n, int \nexp\n);

scalbln(), scalblnf(), scalblnl():

\n
    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
\n
        || /* Since glibc 2.19: */ _DEFAULT_SOURCE

scalbn(), scalbnf(), scalbnl():

\n
    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
\n
        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
\n
        || /* 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:

\n
    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 is a NaN, a NaN is returned.

If x is positive infinity (negative infinity), positive infinity (negative infinity) is returned.

If x is +0 (-0), +0 (-0) 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 return 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:

Range error, overflow

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 attributes(7).

STANDARDS#

C11, POSIX.1-2008.

HISTORY#

glibc 2.1. C99, POSIX.1-2001.

HISTORY#

These functions differ from the obsolete functions described in scalb(3) in the type of their second argument. The functions described on this page have a second argument of an integral type, while those in scalb(3) have a second argument of type double.

NOTES#

If FLT_RADIX equals 2 (which is usual), then scalbn() is equivalent to ldexp(3).

BUGS#

Before glibc 2.20, these functions did not set errno for range errors.

SEE ALSO#

ldexp(3), scalb(3)