ldexp(3) — Linux manual page


ldexp(3)                Library Functions Manual                ldexp(3)

NAME         top

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

LIBRARY         top

       Math library (libm, -lm)

SYNOPSIS         top

       #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

       ldexpf(), ldexpl():
           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION         top

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

RETURN VALUE         top

       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

       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         top

       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         top

       For an explanation of the terms used in this section, see
       │ Interface                           Attribute     Value   │
       │ ldexp(), ldexpf(), ldexpl()         │ Thread safety │ MT-Safe │

STANDARDS         top

       C11, POSIX.1-2008.

HISTORY         top

       C99, POSIX.1-2001.

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

SEE ALSO         top

       frexp(3), modf(3), scalbln(3)

Linux man-pages (unreleased)     (date)                         ldexp(3)

Pages that refer to this page: frexp(3)modf(3)scalb(3)scalbln(3)