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* @license Apache-2.0
*
* Copyright (c) 2024 The Stdlib Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
'use strict';
// MODULES //
var reinterpret = require( '@stdlib/strided/base/reinterpret-complex128' );
var cmul = require( '@stdlib/complex/float64/base/mul' ).assign;
var real = require( '@stdlib/complex/float64/real' );
var imag = require( '@stdlib/complex/float64/imag' );
// MAIN //
/**
* Scales a double-precision complex floating-point vector by a double-precision complex floating-point constant.
*
* @param {PositiveInteger} N - number of indexed elements
* @param {Complex128} alpha - constant
* @param {Complex128Array} x - input array
* @param {integer} strideX - `x` stride length
* @param {NonNegativeInteger} offsetX - starting `x` index
* @returns {Complex128Array} input array
*
* @example
* var Complex128Array = require( '@stdlib/array/complex128' );
* var Complex128 = require( '@stdlib/complex/float64/ctor' );
*
* var x = new Complex128Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
* var alpha = new Complex128( 2.0, 2.0 );
*
* zscal( 3, alpha, x, 1, 0 );
* // x => <Complex128Array>[ -2.0, 6.0, -2.0, 14.0, -2.0, 22.0 ]
*/
function zscal( N, alpha, x, strideX, offsetX ) {
var view;
var re1;
var im1;
var re2;
var im2;
var sx;
var ix;
var i;
if ( N <= 0 ) {
return x;
}
// Reinterpret the input array as a real-valued array of interleaved real and imaginary components:
view = reinterpret( x, 0 );
// Adjust the stride and offset:
sx = strideX * 2;
ix = offsetX * 2;
// Decompose the input scalar to real and imaginary components:
re1 = real( alpha );
im1 = imag( alpha );
for ( i = 0; i < N; i++ ) {
re2 = view[ ix ];
im2 = view[ ix+1 ];
cmul( re1, im1, re2, im2, view, 1, ix );
ix += sx;
}
return x;
}
// EXPORTS //
module.exports = zscal;
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