# exponent
> Return an integer corresponding to the unbiased exponent of a [double-precision floating-point number][ieee754].
## Usage
```javascript
var exponent = require( '@stdlib/number/float64/base/exponent' );
```
#### exponent( x )
Returns an `integer` corresponding to the unbiased exponent of a [double-precision floating-point number][ieee754].
```javascript
var exp = exponent( 3.14e307 ); // => 2**1021 ~ 1e307
// returns 1021
exp = exponent( 3.14e-307 ); // => 2**-1019 ~ 1e-307
// returns -1019
exp = exponent( -3.14 );
// returns 1
exp = exponent( 0.0 );
// returns -1023
exp = exponent( NaN );
// returns 1024
```
## Examples
```javascript
var randu = require( '@stdlib/random/base/uniform' );
var discreteUniform = require( '@stdlib/random/base/discrete-uniform' );
var pow = require( '@stdlib/math/base/special/pow' );
var exponent = require( '@stdlib/number/float64/base/exponent' );
var frac;
var exp;
var x;
var e;
var i;
// Generate random numbers and extract their exponents...
for ( i = 0; i < 100; i++ ) {
frac = randu( 0.0, 10.0 );
exp = discreteUniform( -323, 323 );
x = frac * pow( 10.0, exp );
e = exponent( x );
console.log( 'x: %d. unbiased exponent: %d.', x, e );
}
```
* * *
## C APIs
### Usage
```c
#include "stdlib/number/float64/base/exponent.h"
```
#### stdlib_base_float64_exponent( x )
Returns an integer corresponding to the unbiased exponent of a [double-precision floating-point number][ieee754].
```c
#include
int32_t out = stdlib_base_float64_exponent( 3.14 );
```
The function accepts the following arguments:
- **x**: `[in] double` input value.
```c
int32_t stdlib_base_float64_exponent( const double x );
```
### Examples
```c
#include "stdlib/number/float64/base/exponent.h"
#include
#include
#include
int main( void ) {
double x[] = { 4.0, 0.0, -0.0, 1.0, -1.0, 3.14, -3.14, 1.0e308, -1.0e308, 1.0/0.0, -1.0/0.0, 0.0/0.0 };
int32_t out;
int i;
for ( i = 0; i < 12; i++ ) {
out = stdlib_base_float64_exponent( x[ i ] );
printf( "%lf => out: %" PRId32 "\n", x[ i ], out );
}
}
```
[ieee754]: https://en.wikipedia.org/wiki/IEEE_754-1985
[@stdlib/number/float32/base/exponent]: https://github.com/stdlib-js/number/tree/main/float32/base/exponent