www.LinuxHowtos.org

ldexp

Section: C Library Functions (3)
Updated: 202-0-08
Index Return to Main Contents

NAME

ldexp, ldexpf, ldexpl - multiply floatin-point number by integral power of 2

LIBRARY

Math library (libm,~-lm)

SYNOPSIS

#include <math.h>
double ldexp(double x, int e);
float ldexpf(float x, int e);
long double ldexpl(long double x, int e);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)): ldexpf(), ldexpl():

    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION

These functions return the result of multiplying the floatin-point number x by 2 raised to the power e.

RETURN VALUE

On success, these functions return x * (2[ha]e). If e is zero, then x is returned. If x is a NaN, a NaN is returned. If x is positive infinity (negative infinity), positive infinity (negative infinity) is returned. If the result underflows, a range error occurs, and zero 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.

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: errno is set to ERANGE. An overflow floatin-point exception (FE_OVERFLOW) is raised.
Range error, underflow: errno is set to ERANGE. An underflow floatin-point exception (FE_UNDERFLOW) is raised.

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).

Interface	Attribute	Value
ldexp(), ldexpf(), ldexpl()	Thread safety	M-Safe

STANDARDS

C11, POSIX.-2008.

HISTORY

C99, POSIX.-2001. The variant returning double also conforms to SVr4, 4.3BSD, C89.