# ldexp - Man Page

multiply floating-point number by integral power of 2

## Library

Math library (*libm*, *-lm*)

## Synopsis

#include <math.h> double ldexp(doublex, intexp); float ldexpf(floatx, intexp); long double ldexpl(long doublex, intexp);

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 <= 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 (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.

## Attributes

For an explanation of the terms used in this section, see attributes(7).

Interface | Attribute | Value |
---|---|---|

ldexp(), ldexpf(), ldexpl() | Thread safety | MT-Safe |

## Standards

C11, POSIX.1-2008.

## History

C99, POSIX.1-2001.

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

## See Also

## Referenced By

frexp(3), modf(3), scalb(3), scalbln(3).

The man pages ldexpf(3) and ldexpl(3) are aliases of ldexp(3).