# man pages section 3: Extended Library Functions, Volume 2

Updated: Thursday, June 13, 2019

## ldexpf(3M)

### Name

ldexp, ldexpf, ldexpl - load exponent of a floating point number

### Synopsis

```c99 [ flag... ] file... –lm [ library... ]
#include <math.h>

double ldexp(double x, int exp);```
`float ldexpf(float x, int exp);`
`long double ldexpl(long double x, int exp);`

### Description

These functions computes the quantity x * 2exp.

### Return Values

Upon successful completion, these functions return x multiplied by 2 raised to the power exp.

If these functions would cause overflow, a range error occurs and ldexp(), ldexpf(), and ldexpl() return ±HUGE_VAL, ±HUGE_VALF, and ±HUGE_VALL (according to the sign of x), respectively.

If x is NaN, a NaN is returned.

If x is ±0 or ±Inf, x is returned.

If exp is 0, x is returned.

### Errors

These functions will fail if:

Range Error

The result overflows.

If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, the overflow floating-point exception is raised.

The ldexp() function sets errno to ERANGE if the result overflows.

### Usage

An application wanting to check for exceptions should call feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an exception has been raised. An application should either examine the return value or check the floating point exception flags to detect exceptions.

An application can also set errno to 0 before calling ldexp(). On return, if errno is non-zero, an error has occurred. The ldexpf() and ldexpl() functions do not set errno.

### Attributes

See attributes(7) for descriptions of the following attributes:

ATTRIBUTE TYPE
ATTRIBUTE VALUE
Interface Stability
Committed
Availability
system/library/math
MT-Level
MT-Safe
Standard