npm package: @stdlib/number-float64-base-signbit
Description: Return a boolean indicating if the sign bit for a double-precision floating-point number is on (true) or off (false).
Author: The Stdlib Authors
Latest version: 0.2.4

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# signbit

[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] <!-- [![dependencies][dependencies-image]][dependencies-url] -->

> Return a boolean indicating if the sign bit for a [double-precision floating-point number][ieee754] is on (true) or off (false).

<section class="installation">

## Installation

```bash
npm install @stdlib/number-float64-base-signbit
```

</section>

<section class="usage">

## 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
```

</section>

<!-- /.usage -->

<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```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 );
}
```

</section>

<!-- /.examples -->

<!-- C interface documentation. -->

* * *

<section class="c">

## C APIs

<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->

<section class="intro">

</section>

<!-- /.intro -->

<!-- C usage documentation. -->

<section class="usage">

### Usage

```c
#include "stdlib/number/float64/base/signbit.h"
```

#### stdlib_base_float64_signbit( x )

Returns an integer indicating whether the sign bit for a double-precision floating-point number is on (`1`) or off (`0`).

```c
#include <stdint.h>

int8_t out = stdlib_base_float64_signbit( 3.14 );
```

The function accepts the following arguments:

-   **x**: `[in] double` input value.

```c
int8_t stdlib_base_float64_signbit( const double x );
```

</section>

<!-- /.usage -->

<!-- C API usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="notes">

</section>

<!-- /.notes -->

<!-- C API usage examples. -->

<section class="examples">

### Examples

```c
#include "stdlib/number/float64/base/signbit.h"
#include <stdint.h>
#include <stdio.h>
#include <inttypes.h>

int main( void ) {
    double x[] = { 3.14, -3.14, 0.0, -0.0, 4.0, 1.0, -1.0, 1.0e308, -1.0e308 };

    int8_t out;
    int i;
    for ( i = 0; i < 9; i++ ) {
        stdlib_base_float64_signbit( x[ i ], &out );
        printf( "%lf => signbit: %" PRId8 "\n", x[ i ], out );
    }
}
```

</section>

<!-- /.examples -->

</section>

<!-- /.c -->

<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/number-float32/base/signbit`][@stdlib/number/float32/base/signbit]</span><span class="delimiter">: </span><span class="description">return a boolean indicating if the sign bit for a single-precision floating-point number is on (true) or off (false).</span>

</section>

<!-- /.related -->

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<section class="main-repo" >

* * *

## Notice

This package is part of [stdlib][stdlib], a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop [stdlib][stdlib], see the main project [repository][stdlib].

#### Community

[![Chat][chat-image]][chat-url]

---

## License

See [LICENSE][stdlib-license].


## Copyright

Copyright &copy; 2016-2026. The Stdlib [Authors][stdlib-authors].

</section>

<!-- /.stdlib -->

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[umd]: https://github.com/umdjs/umd
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[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/number-float64-base-signbit/main/LICENSE

[ieee754]: https://en.wikipedia.org/wiki/IEEE_754-1985

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[@stdlib/number/float32/base/signbit]: https://www.npmjs.com/package/@stdlib/number-float32-base-signbit

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</section>

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