npm package: @stdlib/math-base-special-trunc2
Description: Round a numeric value to the nearest power of two toward zero.
Author: The Stdlib Authors
Latest version: 0.3.1

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# trunc2

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> Round a numeric value to the nearest power of two toward zero.

<section class="installation">

## Installation

```bash
npm install @stdlib/math-base-special-trunc2
```

</section>

<section class="usage">

## Usage

```javascript
var trunc2 = require( '@stdlib/math-base-special-trunc2' );
```

#### trunc2( x )

Rounds a `numeric` value to the nearest power of two toward zero.

```javascript
var v = trunc2( -4.2 );
// returns -4.0

v = trunc2( -4.5 );
// returns -4.0

v = trunc2( -4.6 );
// returns -4.0

v = trunc2( 9.99999 );
// returns 8.0

v = trunc2( 9.5 );
// returns 8.0

v = trunc2( 13.0 );
// returns 8.0

v = trunc2( -13.0 );
// returns -8.0

v = trunc2( 0.0 );
// returns 0.0

v = trunc2( -0.0 );
// returns -0.0

v = trunc2( Infinity );
// returns Infinity

v = trunc2( -Infinity );
// returns -Infinity

v = trunc2( NaN );
// returns NaN
```

</section>

<!-- /.usage -->

<section class="examples">

## Examples

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

```javascript
var uniform = require( '@stdlib/random-array-uniform' );
var logEachMap = require( '@stdlib/console-log-each-map' );
var trunc2 = require( '@stdlib/math-base-special-trunc2' );

var opts = {
    'dtype': 'float64'
};
var x = uniform( 100, -50.0, 50.0, opts );

logEachMap( 'x: %0.4f. Rounded: %0.4f.', x, trunc2 );
```

</section>

<!-- /.examples -->

<!-- C interface documentation. -->

* * *

<section class="c">

## C APIs

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<section class="intro">

</section>

<!-- /.intro -->

<!-- C usage documentation. -->

<section class="usage">

### Usage

```c
#include "stdlib/math/base/special/trunc2.h"
```

#### stdlib_base_trunc2( x )

Rounds a `numeric` value to the nearest power of two toward zero.

```c
double y = stdlib_base_trunc2( -4.2 );
// returns -4.0
```

The function accepts the following arguments:

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

```c
double stdlib_base_trunc2( 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/math/base/special/trunc2.h"
#include <stdio.h>

int main( void ) {
    const double x[] = { 3.14, -3.14, 0.0, 0.0 / 0.0 };

    double y;
    int i;
    for ( i = 0; i < 4; i++ ) {
        y = stdlib_base_trunc2( x[ i ] );
        printf( "trunc2(%lf) = %lf\n", x[ i ], y );
    }
}
```

</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/math-base/special/ceil2`][@stdlib/math/base/special/ceil2]</span><span class="delimiter">: </span><span class="description">round a numeric value to the nearest power of two toward positive infinity.</span>
-   <span class="package-name">[`@stdlib/math-base/special/floor2`][@stdlib/math/base/special/floor2]</span><span class="delimiter">: </span><span class="description">round a numeric value to the nearest power of two toward negative infinity.</span>
-   <span class="package-name">[`@stdlib/math-base/special/round2`][@stdlib/math/base/special/round2]</span><span class="delimiter">: </span><span class="description">round a numeric value to the nearest power of two on a linear scale.</span>
-   <span class="package-name">[`@stdlib/math-base/special/trunc`][@stdlib/math/base/special/trunc]</span><span class="delimiter">: </span><span class="description">round a double-precision floating-point number toward zero.</span>
-   <span class="package-name">[`@stdlib/math-base/special/trunc10`][@stdlib/math/base/special/trunc10]</span><span class="delimiter">: </span><span class="description">round a numeric value to the nearest power of 10 toward zero.</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

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---

## License

See [LICENSE][stdlib-license].


## Copyright

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

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<!-- <related-links> -->

[@stdlib/math/base/special/ceil2]: https://www.npmjs.com/package/@stdlib/math-base-special-ceil2

[@stdlib/math/base/special/floor2]: https://www.npmjs.com/package/@stdlib/math-base-special-floor2

[@stdlib/math/base/special/round2]: https://www.npmjs.com/package/@stdlib/math-base-special-round2

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