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feat: add blas/base/cscal
PR-URL: stdlib-js#2104 Ref: stdlib-js#2039 Co-authored-by: Athan Reines <[email protected]> Reviewed-by: Athan Reines <[email protected]> Signed-off-by: Athan Reines <[email protected]>
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‎lib/node_modules/@stdlib/blas/base/cscal/README.md

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<!--
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@license Apache-2.0
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Copyright (c) 2024 The Stdlib Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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# cscal
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> Scales a single-precision complex floating-point vector by a single-precision complex floating-point constant.
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<section class="usage">
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## Usage
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```javascript
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var cscal = require( '@stdlib/blas/base/cscal' );
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```
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#### cscal( N, ca, cx, strideX )
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Scales values from `cx` by `ca`.
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```javascript
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var Complex64Array = require( '@stdlib/array/complex64' );
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var Complex64 = require( '@stdlib/complex/float32/ctor' );
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var realf = require( '@stdlib/complex/realf' );
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var imagf = require( '@stdlib/complex/imagf' );
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var cx = new Complex64Array( [ 1.0, 1.0, 1.0, 1.0, 1.0, 1.0 ] );
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var ca = new Complex64( 2.0, 0.0 );
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cscal( 3, ca, cx, 1 );
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var z = cx.get( 0 );
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// returns <Complex64>
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var re = realf( z );
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// returns 2.0
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var im = imagf( z );
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// returns 2.0
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```
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The function has the following parameters:
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- **N**: number of indexed elements.
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- **ca**: scalar [`Complex64`][@stdlib/complex/float32/ctor] constant.
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- **cx**: input [`Complex64Array`][@stdlib/array/complex64].
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- **strideX**: index increment for `cx`.
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The `N` and stride parameters determine how values from `cx` are scaled by `ca`. For example, to scale every other value in `cx` by `ca`,
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```javascript
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var Complex64Array = require( '@stdlib/array/complex64' );
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var Complex64 = require( '@stdlib/complex/float32/ctor' );
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var realf = require( '@stdlib/complex/realf' );
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var imagf = require( '@stdlib/complex/imagf' );
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var cx = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );
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var ca = new Complex64( 2.0, 0.0 );
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cscal( 2, ca, cx, 2 );
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var z = cx.get( 2 );
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// returns <Complex64>
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var re = realf( z );
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// returns 10.0
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var im = imagf( z );
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// returns 12.0
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```
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Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views.
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<!-- eslint-disable stdlib/capitalized-comments -->
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```javascript
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var Complex64Array = require( '@stdlib/array/complex64' );
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var Complex64 = require( '@stdlib/complex/float32/ctor' );
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var realf = require( '@stdlib/complex/realf' );
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var imagf = require( '@stdlib/complex/imagf' );
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// Initial array:
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var cx0 = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );
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// Define a scalar constant:
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var ca = new Complex64( 2.0, 2.0 );
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// Create an offset view:
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var cx1 = new Complex64Array( cx0.buffer, cx0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
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// Scales every other value from `cx1` by `ca`...
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cscal( 3, ca, cx1, 1 );
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var z = cx0.get( 1 );
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// returns <Complex64>
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var re = realf( z );
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// returns -2.0
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var im = imagf( z );
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// returns 14.0
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```
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#### cscal.ndarray( N, ca, cx, strideX, offsetX )
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Scales values from `cx` by `ca` using alternative indexing semantics.
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```javascript
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var Complex64Array = require( '@stdlib/array/complex64' );
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var Complex64 = require( '@stdlib/complex/float32/ctor' );
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var realf = require( '@stdlib/complex/realf' );
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var imagf = require( '@stdlib/complex/imagf' );
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var cx = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
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var ca = new Complex64( 2.0, 2.0 );
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cscal.ndarray( 3, ca, cx, 1, 0 );
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var z = cx.get( 0 );
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// returns <Complex64>
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var re = realf( z );
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// returns -2.0
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var im = imagf( z );
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// returns 6.0
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```
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The function has the following additional parameters:
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- **offsetX**: starting index for `cx`.
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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 scale every other value in the input strided array starting from the second element,
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```javascript
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var Complex64Array = require( '@stdlib/array/complex64' );
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var Complex64 = require( '@stdlib/complex/float32/ctor' );
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var realf = require( '@stdlib/complex/realf' );
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var imagf = require( '@stdlib/complex/imagf' );
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var cx = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );
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var ca = new Complex64( 2.0, 2.0 );
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cscal.ndarray( 2, ca, cx, 2, 1 );
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var z = cx.get( 3 );
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// returns <Complex64>
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var re = realf( z );
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// returns -2.0
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var im = imagf( z );
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// returns 30.0
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```
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</section>
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<!-- /.usage -->
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<section class="notes">
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## Notes
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- If `N <= 0` or `strideX <= 0` , both functions return `cx` unchanged.
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- `cscal()` corresponds to the [BLAS][blas] level 1 function [`cscal`][cscal].
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</section>
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<!-- /.notes -->
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<section class="examples">
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## Examples
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<!-- eslint no-undef: "error" -->
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```javascript
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var discreteUniform = require( '@stdlib/random/base/discrete-uniform' );
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var filledarrayBy = require( '@stdlib/array/filled-by' );
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var Complex64 = require( '@stdlib/complex/float32/ctor' );
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var cscal = require( '@stdlib/blas/base/cscal' );
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function rand() {
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return new Complex64( discreteUniform( 0, 10 ), discreteUniform( -5, 5 ) );
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}
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var cx = filledarrayBy( 10, 'complex64', rand );
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console.log( cx.toString() );
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var ca = new Complex64( 2.0, 2.0 );
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console.log( ca.toString() );
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// Scale elements from `cx` by `ca`:
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cscal( cx.length, ca, cx, 1 );
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console.log( cx.get( cx.length-1 ).toString() );
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```
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</section>
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<!-- /.examples -->
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<!-- C interface documentation. -->
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* * *
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<section class="c">
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## C APIs
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<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->
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<section class="intro">
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</section>
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<!-- /.intro -->
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<!-- C usage documentation. -->
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<section class="usage">
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### Usage
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```c
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#include "stdlib/blas/base/cscal.h"
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```
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#### c_cscal( N, ca, \*CX, strideX )
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Scales values from `CX` by `ca`.
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```c
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#include "stdlib/complex/float32/ctor.h"
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float cx[] = { 1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 6.0f, 7.0f, 8.0f };
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const stdlib_complex64_t ca = stdlib_complex64( 2.0f, 2.0f );
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c_dscal( 4, ca, (void *)cx, 1 );
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```
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The function accepts the following arguments:
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- **N**: `[in] CBLAS_INT` number of indexed elements.
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- **ca**: `[in] stdlib_complex64_t` scalar constant.
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- **CX**: `[inout] void*` input array.
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- **strideX**: `[in] CBLAS_INT` index increment for `CX`.
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```c
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void c_dscal( const CBLAS_INT N, const stdlib_complex64_t ca, void *CX, const CBLAS_INT strideX );
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```
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</section>
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<!-- /.usage -->
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<!-- C API usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="notes">
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</section>
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<!-- /.notes -->
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<!-- C API usage examples. -->
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<section class="examples">
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### Examples
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```c
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#include "stdlib/blas/base/cscal.h"
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#include "stdlib/complex/float32/ctor.h"
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#include <stdio.h>
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int main( void ) {
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// Create a strided array of interleaved real and imaginary components:
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float cx[] = { 1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 6.0f, 7.0f, 8.0f };
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// Create a complex scalar:
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const stdlib_complex64_t ca = stdlib_complex64( 2.0f, 2.0f );
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// Specify the number of elements:
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const int N = 4;
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// Specify stride length:
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const int strideX = 1;
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// Scale the elements of the array:
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c_cscal( N, ca, (void *)cx, strideX );
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// Print the result:
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for ( int i = 0; i < N; i++ ) {
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printf( "cx[ %i ] = %f + %fj\n", i, cx[ i*2 ], cx[ (i*2)+1 ] );
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}
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}
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```
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</section>
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<!-- /.examples -->
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</section>
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<!-- /.c -->
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<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->
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<section class="related">
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</section>
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<!-- /.related -->
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<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="links">
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[blas]: http://www.netlib.org/blas
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[cscal]: http://www.netlib.org/lapack/explore-html/da/df6/group__complex__blas__level1.html
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[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray
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[@stdlib/array/complex64]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/array/complex64
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[@stdlib/complex/float32/ctor]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/complex/float32/ctor
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</section>
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<!-- /.links -->

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