### 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**(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; or
*cc -std=c99*

### 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, an 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

### COLOPHON

This page is part of release 3.23 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/.