main.js

/**
* @license Apache-2.0
*
* Copyright (c) 2026 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 numelDimension = require( '@stdlib/ndarray-base-numel-dimension' );
var getStrides = require( '@stdlib/ndarray-base-strides' );
var getStride = require( '@stdlib/ndarray-base-stride' );
var getOffset = require( '@stdlib/ndarray-base-offset' );
var getData = require( '@stdlib/ndarray-base-data-buffer' );
var ndarraylike2scalar = require( '@stdlib/ndarray-base-ndarraylike2scalar' );
var strided = require( '@stdlib/blas-base-ssyr' ).ndarray;


// MAIN //

/**
* Performs the symmetric rank 1 operation `A = alpha*x*x^T + A`, where `alpha` is a scalar, `x` is a one-dimensional ndarray, and `A` is an `N` by `N` symmetric matrix.
*
* ## Notes
*
* -   The function expects the following ndarrays:
*
*     -   a one-dimensional input ndarray corresponding to `x`.
*     -   a two-dimensional input/output ndarray corresponding to `A`.
*     -   a zero-dimensional ndarray specifying whether the upper or lower triangular part of the symmetric matrix `A` should be referenced.
*     -   a zero-dimensional ndarray containing a scalar constant corresponding to `alpha`.
*
* @param {ArrayLikeObject<Object>} arrays - array-like object containing ndarrays
* @returns {Object} output ndarray
*
* @example
* var Float32Matrix = require( '@stdlib/ndarray-matrix-float32' );
* var Float32Vector = require( '@stdlib/ndarray-vector-float32' );
* var scalar2ndarray = require( '@stdlib/ndarray-from-scalar' );
* var resolveEnum = require( '@stdlib/blas-base-matrix-triangle-resolve-enum' );
*
* var x = new Float32Vector( [ 1.0, 2.0, 3.0 ] );
* var A = new Float32Matrix( [ [ 1.0, 2.0, 3.0 ], [ 2.0, 1.0, 2.0 ], [ 3.0, 2.0, 1.0 ] ] );
*
* var uplo = scalar2ndarray( resolveEnum( 'upper' ), {
*     'dtype': 'int32'
* });
* var alpha = scalar2ndarray( 1.0, {
*     'dtype': 'float32'
* });
*
* var y = ssyr( [ x, A, uplo, alpha ] );
* // returns <ndarray>[ [ 2.0, 4.0, 6.0 ], [ 2.0, 5.0, 8.0 ], [ 3.0, 2.0, 10.0 ] ]
*
* var bool = ( y === A );
* // returns true
*/
function ssyr( arrays ) {
	var alpha;
	var uplo;
	var st;
	var x;
	var A;

	x = arrays[ 0 ];
	A = arrays[ 1 ];

	uplo = ndarraylike2scalar( arrays[ 2 ] );
	alpha = ndarraylike2scalar( arrays[ 3 ] );

	st = getStrides( A, false );

	strided( uplo, numelDimension( A, 0 ), alpha, getData( x ), getStride( x, 0 ), getOffset( x ), getData( A ), st[ 0 ], st[ 1 ], getOffset( A ) );

	return A;
}


// EXPORTS //

module.exports = ssyr;