# scalbn(), scalbnf(), scalbnl()

## Synopsis:

```#include <math.h>

double scalbn ( double x,
int n );

float scalbnf ( float x,
int n );

long double scalbnl ( long double x,
int n );
```

## Arguments:

x
The floating point number that you want to multiply by the exponent.
n
The exponent to apply to the radix of the machine's floating-point arithmetic.

## Library:

libm

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

## Description:

The scalbn(), scalbnf(), and scalbnl() functions compute x × rn, where r is the radix of the machine's floating-point arithmetic. The difference between the scalbn* and scalbln* functions is the type of the second argument.

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

• Call feclearexcept(FE_ALL_EXCEPT) before calling scalbn(), scalbnf(), or scalbnl().
• On return, if fetestexcept(FE_ALL_EXCEPT) is nonzero, then an error has occurred.

## Returns:

x × rn

If: These functions return: Errors:
x is NaN NaN
x is ±0.0 or ±Inf x
n is 0 x
The correct value would cause underflow The correct value, after rounding FE_UNDERFLOW
The correct value would cause overflow Inf FE_OVERFLOW

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 <inttypes.h>
#include <math.h>
#include <fenv.h>
#include <stdlib.h>

int main( void )
{
double a, b, c, d;
int except_flags;

feclearexcept(FE_ALL_EXCEPT);
a = 10;
b = 2;
c = scalbn(a, b);

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

feclearexcept(FE_ALL_EXCEPT);

d = sqrt(c/a);

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

printf("Radix of machine's fp arithmetic is %f \n", d);
printf("So %f = %f * (%f ^ %f) \n", c, a, d, b);

return EXIT_SUCCESS;
}
```

produces the output:

```Radix of machine's fp arithmetic is 2.000000
So 40.000000 = 10.000000 * (2.000000 ^ 2.000000)
```

## Classification:

Safety:
Cancellation point No
Interrupt handler No
Signal handler No