# signbit
> Return a boolean indicating if the sign bit for a [double-precision floating-point number][ieee754] is on (true) or off (false).
## Usage
```javascript
var signbit = require( '@stdlib/number/float64/base/signbit' );
```
#### signbit( x )
Returns a `boolean` indicating if the sign bit for a [double-precision floating-point number][ieee754] is on (`true`) or off (`false`).
```javascript
var bool = signbit( 4.0 );
// returns false
bool = signbit( -9.14e-307 );
// returns true
bool = signbit( 0.0 );
// returns false
bool = signbit( -0.0 );
// returns true
```
## Examples
```javascript
var randu = require( '@stdlib/random/base/randu' );
var signbit = require( '@stdlib/number/float64/base/signbit' );
var sign;
var x;
var i;
for ( i = 0; i < 100; i++ ) {
x = ( randu()*100.0 ) - 50.0;
sign = signbit( x );
sign = ( sign ) ? 'true' : 'false';
console.log( 'x: %d. signbit: %s.', x, sign );
}
```
[ieee754]: https://en.wikipedia.org/wiki/IEEE_754-1985