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);
 
[Note] Note
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
ldexpf(), ldexpl():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
or cc -std=c99
[Note] Note

Link with −lm.

DESCRIPTION

The ldexp() function returns 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 (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.

CONFORMING TO

C99, POSIX.1-2001. 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 3.52 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man−pages/.


  Copyright 1993 David Metcalfe (davidprism.demon.co.uk)
and Copyright 2008, Linux Foundation, written by Michael Kerrisk
    <mtk.manpagesgmail.com>

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References consulted:
    Linux libc source code
    Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
    386BSD man pages
Modified 1993-07-24 by Rik Faith (faithcs.unc.edu)
Modified 2004-10-31 by aeb