npm package: @stdlib/math-base-special-croundn
Description: Round each component of a double-precision complex floating-point number to the nearest multiple of 10^n.
Author: The Stdlib Authors
Latest version: 0.2.3

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# croundn

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

> Round each component of a double-precision complex floating-point number to the nearest multiple of `10^n`.

<section class="installation">

## Installation

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

</section>

<section class="usage">

## Usage

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

#### croundn( z, n )

Rounds each component of a double-precision complex floating-point number to the nearest multiple of `10^n`.

```javascript
var Complex128 = require( '@stdlib/complex-float64-ctor' );

var v = croundn( new Complex128( -3.141592653589793, 3.141592653589793 ), -2 );
// returns <Complex128>[ -3.14, 3.14 ]

v = croundn( new Complex128( -3.141592653589793, 3.141592653589793 ), 0 );
// returns <Complex128>[ -3.0, 3.0 ]

v = croundn( new Complex128( -12368.0, 12368.0 ), 3 );
// returns <Complex128>[ -12000.0, 12000.0 ]

v = croundn( new Complex128( NaN, NaN ), 3 );
// returns <Complex128>[ NaN, NaN ]
```

</section>

<!-- /.usage -->

<section class="notes">

## Notes

-   When operating on [floating-point numbers][ieee754] in bases other than `2`, rounding to specified digits can be **inexact**. For example,

    ```javascript
    var Complex128 = require( '@stdlib/complex-float64-ctor' );

    var x = 0.2 + 0.1;
    // returns 0.30000000000000004

    // Should round components to 0.3:
    var v = croundn( new Complex128( x, x ), -16 );
    // returns <Complex128>[ 0.3000000000000001, 0.3000000000000001 ]
    ```

</section>

<!-- /.notes -->

<section class="examples">

## Examples

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

```javascript
var uniform = require( '@stdlib/random-base-uniform' ).factory;
var Complex128 = require( '@stdlib/complex-float64-ctor' );
var floor = require( '@stdlib/math-base-special-floor' );
var croundn = require( '@stdlib/math-base-special-croundn' );

var rand1 = uniform( -5.0, 0.0 );
var rand2 = uniform( -50.0, 50.0 );

var z;
var i;
var n;
for ( i = 0; i < 100; i++ ) {
    z = new Complex128( rand2(), rand2() );
    n = floor( rand1() );
    console.log( 'croundn(%s, %s) = %s', z, n, croundn( z, n ) );
}
```

</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/croundn.h"
```

#### stdlib_base_croundn( z, n )

Rounds each component of a double-precision complex floating-point number to the nearest multiple of `10^n`.

```c
#include "stdlib/complex/float64/ctor.h"
#include "stdlib/complex/float64/real.h"
#include "stdlib/complex/float64/imag.h"

stdlib_complex128_t z = stdlib_complex128( -3.141592653589793, 3.141592653589793 );

stdlib_complex128_t out = stdlib_base_croundn( z, -2 );

double re = stdlib_complex128_real( out );
// returns -3.14

double im = stdlib_complex128_imag( out );
// returns 3.14
```

The function accepts the following arguments:

-   **z**: `[in] stdlib_complex128_t` input value.
-   **n**: `[in] int32_t` integer power of 10.

```c
stdlib_complex128_t stdlib_base_croundn( const stdlib_complex128_t z, const int32_t n );
```

</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/croundn.h"
#include "stdlib/complex/float64/ctor.h"
#include "stdlib/complex/float64/reim.h"
#include <stdio.h>

int main( void ) {
    const stdlib_complex128_t x[] = {
        stdlib_complex128( 3.14, 1.5 ),
        stdlib_complex128( -3.14, -1.5 ),
        stdlib_complex128( 0.0, 0.0 ),
        stdlib_complex128( 0.0/0.0, 0.0/0.0 )
    };

    stdlib_complex128_t v;
    stdlib_complex128_t y;
    double re1;
    double im1;
    double re2;
    double im2;
    int i;
    for ( i = 0; i < 4; i++ ) {
        v = x[ i ];
        y = stdlib_base_croundn( v, -2 );
        stdlib_complex128_reim( v, &re1, &im1 );
        stdlib_complex128_reim( y, &re2, &im2 );
        printf( "croundn(%lf + %lfi) = %lf + %lfi\n", re1, im1, re2, im2 );
    }
}
```

</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/cceiln`][@stdlib/math/base/special/cceiln]</span><span class="delimiter">: </span><span class="description">round each component of a double-precision complex floating-point number to the nearest multiple of 10^n toward positive infinity.</span>
-   <span class="package-name">[`@stdlib/math-base/special/cfloorn`][@stdlib/math/base/special/cfloorn]</span><span class="delimiter">: </span><span class="description">round each component of a double-precision complex floating-point number to the nearest multiple of 10^n toward negative infinity.</span>
-   <span class="package-name">[`@stdlib/math-base/special/cround`][@stdlib/math/base/special/cround]</span><span class="delimiter">: </span><span class="description">round each component of a double-precision complex floating-point number to the nearest integer.</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].

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---

## License

See [LICENSE][stdlib-license].


## Copyright

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

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

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

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

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

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