npm package: @stdlib/blas-ext-base-zfill
Description: Fill a double-precision complex floating-point strided array with a specified scalar constant.
Author: The Stdlib Authors
Latest version: 0.1.1

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# zfill

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> Fill a double-precision complex floating-point strided array with a specified scalar constant.

<section class="installation">

## Installation

```bash
npm install @stdlib/blas-ext-base-zfill
```

</section>

<section class="usage">

## Usage

```javascript
var zfill = require( '@stdlib/blas-ext-base-zfill' );
```

#### zfill( N, alpha, x, strideX )

Fills a double-precision complex floating-point strided array `x` with a specified scalar constant `alpha`.

```javascript
var Float64Array = require( '@stdlib/array-float64' );
var Complex128Array = require( '@stdlib/array-complex128' );
var Complex128 = require( '@stdlib/complex-float64-ctor' );

var arr = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );
var x = new Complex128Array( arr );

var alpha = new Complex128( 10.0, 10.0 );

zfill( x.length, alpha, x, 1 );

var y = x.get( 0 );
// returns <Complex128>[ 10.0, 10.0 ]
```

The function has the following parameters:

-   **N**: number of indexed elements.
-   **alpha**: scalar constant.
-   **x**: input [`Complex128Array`][@stdlib/array/complex128].
-   **strideX**: index increment.

The `N` and stride parameters determine which elements in the strided array are accessed at runtime. For example, to fill every other element

```javascript
var Float64Array = require( '@stdlib/array-float64' );
var Complex128Array = require( '@stdlib/array-complex128' );
var Complex128 = require( '@stdlib/complex-float64-ctor' );

var arr = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );
var x = new Complex128Array( arr );

var alpha = new Complex128( 10.0, 10.0 );

zfill( 2, alpha, x, 2 );

var y = x.get( 0 );
// returns <Complex128>[ 10.0, 10.0 ]

y = x.get( 1 );
// returns <Complex128>[ 3.0, 4.0 ]
```

Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views.

```javascript
var Float64Array = require( '@stdlib/array-float64' );
var Complex128Array = require( '@stdlib/array-complex128' );
var Complex128 = require( '@stdlib/complex-float64-ctor' );

// Create the underlying floating-point array:
var arr = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );

// Initial array:
var x0 = new Complex128Array( arr );

// Create an offset view:
var x1 = new Complex128Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

// Define a scalar constant:
var alpha = new Complex128( 10.0, 10.0 );

// Fill every other element:
zfill( 2, alpha, x1, 2 );

var y = x0.get( 0 );
// returns <Complex128>[ 1.0, 2.0 ]

y = x0.get( 1 );
// returns <Complex128>[ 10.0, 10.0 ]
```

#### zfill.ndarray( N, alpha, x, strideX, offsetX )

Fills a double-precision complex floating-point strided array `x` with a specified scalar constant `alpha` using alternative indexing semantics.

```javascript
var Float64Array = require( '@stdlib/array-float64' );
var Complex128Array = require( '@stdlib/array-complex128' );
var Complex128 = require( '@stdlib/complex-float64-ctor' );

var arr = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );
var x = new Complex128Array( arr );

var alpha = new Complex128( 10.0, 10.0 );

zfill.ndarray( x.length, alpha, x, 1, 0 );

var y = x.get( 0 );
// returns <Complex128>[ 10.0, 10.0 ]
```

The function has the following additional parameters:

-   **offsetX**: starting index.

While [`typed array`][mdn-typed-array] views mandate a view offset based on the underlying buffer, the offset parameter supports indexing semantics based on a starting index. For example, to access only the last two elements of the strided array

```javascript
var Float64Array = require( '@stdlib/array-float64' );
var Complex128Array = require( '@stdlib/array-complex128' );
var Complex128 = require( '@stdlib/complex-float64-ctor' );

var arr = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var x = new Complex128Array( arr );

var alpha = new Complex128( 10.0, 10.0 );

zfill.ndarray( 2, alpha, x, 1, x.length-2 );

var y = x.get( 0 );
// returns <Complex128>[ 1.0, 2.0 ]

y = x.get( 1 );
// returns <Complex128>[ 10.0, 10.0 ]

y = x.get( 2 );
// returns <Complex128>[ 10.0, 10.0 ]
```

</section>

<!-- /.usage -->

<section class="notes">

## Notes

-   If `N <= 0`, both functions return the strided array unchanged.

</section>

<!-- /.notes -->

<section class="examples">

## Examples

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

```javascript
var discreteUniform = require( '@stdlib/random-array-discrete-uniform' );
var Complex128 = require( '@stdlib/complex-float64-ctor' );
var Complex128Array = require( '@stdlib/array-complex128' );
var zfill = require( '@stdlib/blas-ext-base-zfill' );

var xbuf = discreteUniform( 20, -100, 100, {
    'dtype': 'float64'
});
var x = new Complex128Array( xbuf.buffer );
var alpha = new Complex128( 10.0, 10.0 );

zfill( x.length, alpha, x, 1 );
console.log( x.get( 0 ).toString() );
```

</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/blas/ext/base/zfill.h"
```

#### stdlib_strided_zfill( N, alpha, \*X, strideX )

Fills a double-precision complex floating-point strided array `X` with a specified scalar constant `alpha`.

```c
double x[] = { 1.0, 2.0, 3.0, 4.0 };
const stdlib_complex128_t alpha = stdlib_complex128( 2.0, 2.0 );

stdlib_strided_zfill( 2, alpha, (stdlib_complex128_t *)x, 1 );
```

The function accepts the following arguments:

-   **N**: `[in] CBLAS_INT` number of indexed elements.
-   **alpha**: `[in] stdlib_complex128_t` scalar constant.
-   **X**: `[out] stdlib_complex128_t*` input array.
-   **strideX**: `[in] CBLAS_INT` index increment for `X`.

```c
void stdlib_strided_zfill( const CBLAS_INT N, const stdlib_complex128_t alpha, stdlib_complex128_t *X, const CBLAS_INT strideX );
```

#### stdlib_strided_zfill_ndarray( N, alpha, \*X, strideX, offsetX )

Fills a double-precision complex floating-point strided array `X` with a specified scalar constant `alpha` using alternative indexing semantics.

```c
double x[] = { 1.0, 2.0, 3.0, 4.0 };
const stdlib_complex128_t alpha = stdlib_complex128( 2.0, 2.0 );

stdlib_strided_zfill_ndarray( 4, alpha, (stdlib_complex128_t *)x, 1, 0 );
```

The function accepts the following arguments:

-   **N**: `[in] CBLAS_INT` number of indexed elements.
-   **alpha**: `[in] stdlib_complex128_t` scalar constant.
-   **X**: `[out] stdlib_complex128_t*` input array.
-   **strideX**: `[in] CBLAS_INT` index increment for `X`.
-   **offsetX**: `[in] CBLAS_INT` starting index for `X`.

```c
void stdlib_strided_zfill_ndarray( const CBLAS_INT N, const stdlib_complex128_t alpha, stdlib_complex128_t *X, const CBLAS_INT strideX, const CBLAS_INT offsetX );
```

</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/complex/float64/ctor.h"
#include "stdlib/blas/ext/base/zfill.h"
#include <stdio.h>

int main() {
    // Create a strided array of interleaved real and imaginary components:
    double x[] = { 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 };

    // Create a scalar constant:
    const stdlib_complex128_t alpha = stdlib_complex128( 2.0, 2.0 );

    // Specify the number of elements:
    const int N = 4;

    // Specify a stride:
    const int strideX = 1;

    // Fill the array:
    stdlib_strided_zfill( N, alpha, (stdlib_complex128_t *)x, strideX );

    // Print the result:
    for ( int i = 0; i < 8; i++ ) {
        printf( "x[ %i ] = %lf\n", i, x[ i ] );
    }
}
```

</section>

<!-- /.examples -->

</section>

<!-- /.c -->

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

<section class="related">

</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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