LDEXP(3)                   Linux Programmer's Manual                  LDEXP(3)



NAME
       ldexp,  ldexpf,  ldexpl  -  multiply  floating-point 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  floating-point
       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 (nega-
       tive 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; lbw27 lb lb  l  l  l.   Interface Attribute Value  T{  ldexp(),
       ldexpf(), ldexpl() T}   Thread safety  MT-Safe

CONFORMING TO
       C99, POSIX.1-2001, POSIX.1-2008.

       The variant returning double also conforms to SVr4, 4.3BSD, C89.

SEE ALSO
       frexp(3), modf(3), scalbln(3)

COLOPHON
       This  page  is  part of release 4.16 of the Linux man-pages project.  A
       description of the project, information about reporting bugs,  and  the
       latest     version     of     this    page,    can    be    found    at
       https://www.kernel.org/doc/man-pages/.



                                  2017-09-15                          LDEXP(3)