# ldexp(), ldexpf(), ldexpl()

Load exponent: multiply a floating-point number by an integral power of 2

## Synopsis:

```#include <math.h>

double ldexp( double x,
int exp );

float ldexp( float x,
int exp );

long double ldexpl( long double x,
int exp );
```

## Arguments:

x
A floating-point number.
exp
The exponent of 2 to multiply x by.

## Library:

libm

Use the -l m option to qcc to link against this library.

## Description:

These functions multiply the floating-point number x by 2exp.

To check for error situations, use feclearexcept() and fetestexcept(). For example:

• Call feclearexcept(FE_ALL_EXCEPT) before calling ldexp(), ldexpf(), or ldexpl().
• On return, if fetestexcept(FE_ALL_EXCEPT) is nonzero, then an error has occurred.

## Returns:

x * 2exp

If: These functions return: Errors:
x is ±0.0 x
x is ±Inf x
x is NaN x
The result would cause overflow Inf FE_OVERFLOW
The correct value would cause underflow The correct value, after rounding

These functions raise FE_INEXACT if the FPU reports that the result can't be exactly represented as a floating-point number.

## Examples:

```#include <stdio.h>
#include <math.h>
#include <fenv.h>
#include <stdlib.h>

int main( void )
{
int except_flags;
double value;

feclearexcept(FE_ALL_EXCEPT);

value = ldexp( 4.7072345, 5 );

except_flags = fetestexcept(FE_ALL_EXCEPT);
if(except_flags) {
/* An error occurred; handle it appropriately. */
}

printf( "%f\n", value );

return EXIT_SUCCESS;
}
```

produces the output:

```150.631504
```

## Classification:

Safety:
Cancellation point No
Interrupt handler No
Signal handler No