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* @license Apache-2.0
*
* Copyright (c) 2025 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';
/**
* LAPACK routine to generate a real elementary reflector `H` of order `N` such that applying `H` to a vector `[alpha; X]` zeros out `X`.
*
* ## Notes
*
* - `H` is a Householder matrix with the form `H = I - tau * [1; V] * [1, V^T]`, where `tau` is a scalar and `V` is a vector.
* - the input vector is `[alpha; X]`, where `alpha` is a scalar and `X` is a real `(n-1)`-element vector.
* - the result of applying `H` to `[alpha; X]` is `[beta; 0]`, with `beta` being a scalar and the rest of the vector zeroed.
* - if all elements of `X` are zero, then `tau = 0` and `H` is the identity matrix.
* - otherwise, `1 <= tau <= 2`
*
* @module @stdlib/lapack/base/dlarfg
*
* @example
* var Float64Array = require( '@stdlib/array/float64' );
* var dlarfg = require( '@stdlib/lapack/base/dlarfg' );
*
* var X = new Float64Array( [ 2.0, 3.0, 4.0 ] );
* var out = new Float64Array( [ 4.0, 0.0 ] );
*
* dlarfg( 4, X, 1, out );
* // X => <Float64Array>[ ~0.19, ~0.28, ~0.37 ]
* // out => <Float64Array>[ ~-6.7, ~1.6 ]
*
* @example
* var Float64Array = require( '@stdlib/array/float64' );
* var dlarfg = require( '@stdlib/lapack/base/dlarfg' );
*
* var X = new Float64Array( [ 2.0, 3.0, 4.0 ] );
* var out = new Float64Array( [ 4.0, 0.0 ] );
*
* dlarfg.ndarray( 4, X, 1, 0, out, 1, 0 );
* // X => <Float64Array>[ ~0.19, ~0.28, ~0.37 ]
* // out => <Float64Array>[ ~-6.7, ~1.6 ]
*/
// MODULES //
var join = require( 'path' ).join;
var tryRequire = require( '@stdlib/utils/try-require' );
var isError = require( '@stdlib/assert/is-error' );
var main = require( './main.js' );
// MAIN //
var dlarfg;
var tmp = tryRequire( join( __dirname, './native.js' ) );
if ( isError( tmp ) ) {
dlarfg = main;
} else {
dlarfg = tmp;
}
// EXPORTS //
module.exports = dlarfg;
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