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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.