ldexp (3)  Linux Man Pages
ldexp: multiply floatingpoint number by integral power of 2
NAME
ldexp, ldexpf, ldexpl  multiply floatingpoint number by integral power of 2
SYNOPSIS
#include <math.h> double ldexp(double x, int exp); float ldexpf(float x, int exp); long double ldexpl(long double x, int exp);
Link with lm.
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 versions <= 2.19: */ _BSD_SOURCE  _SVID_SOURCE
DESCRIPTION
These functions return the result of multiplying the floatingpoint number x by 2 raised to the power exp.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 floatingpoint exception (FE_OVERFLOW) is raised.
 Range error, underflow
 errno is set to ERANGE. An underflow floatingpoint 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  MTSafe 
CONFORMING TO
C99, POSIX.12001, POSIX.12008.The variant returning double also conforms to SVr4, 4.3BSD, C89.
COLOPHON
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