Name
ldexp, ldexpf, ldexpl - multiply floating-point number by integral power of 2Library
Math library ( libm ", " -lm )Synopsis
#include <math.h> double ldexp(double " x ", int exp );
float ldexpf(float " x ", int exp );
long double ldexpl(long double " x ", int exp );
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 floating-point number x by 2 raised to the powerexp. Return Value
On success, these functions return"x * (2^exp)". If exp 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 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). allbox; lbx lb lb T{ ldexp()ldexpf()ldexpl()| Interface | Attribute | Value |
| T} | Thread safety | MT-Safe |
Standards
C11, POSIX.1-2008.History
C99, POSIX.1-2001.The variant returning double also conforms to SVr4, 4.3BSD, C89.