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* @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';
// MAIN //
/**
* Interchanges two columns in a matrix `A`.
*
* ## Notes
*
* - If provided negative column indices, the function resolves the indices relative to the last column, with the last column corresponding to `-1`.
*
* @private
* @param {NonNegativeInteger} M - number of rows in matrix `A`
* @param {NonNegativeInteger} i - index of the first column to interchange
* @param {NonNegativeInteger} j - index of the second column to interchange
* @param {Object} A - input matrix object
* @param {Collection} A.data - input matrix data
* @param {Array<Function>} A.accessors - matrix element accessors
* @param {integer} strideA1 - stride length for the first dimension of `A`
* @param {integer} strideA2 - stride length for the second dimension of `A`
* @param {NonNegativeInteger} offsetA - starting index for `A`
* @returns {Object} `A`
*
* @example
* var toAccessorArray = require( '@stdlib/array/base/to-accessor-array' );
* var arraylike2object = require( '@stdlib/array/base/arraylike2object' );
*
* var A = arraylike2object( toAccessorArray( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] ) );
*
* gswapColumns( 3, 0, 1, A, 2, 1, 0 );
* // A.data => [ 2.0, 1.0, 4.0, 3.0, 6.0, 5.0 ]
*/
function gswapColumns( M, i, j, A, strideA1, strideA2, offsetA ) {
var abuf;
var aget;
var aset;
var tmp;
var ia;
var ja;
var i1;
// Cache a reference to the array data:
abuf = A.data;
// Cache references to the element accessors:
aget = A.accessors[ 0 ];
aset = A.accessors[ 1 ];
ia = offsetA + ( i*strideA2 );
ja = offsetA + ( j*strideA2 );
for ( i1 = 0; i1 < M; i1++ ) {
tmp = aget( abuf, ia );
aset( abuf, ia, aget( abuf, ja ) );
aset( abuf, ja, tmp );
ia += strideA1;
ja += strideA1;
}
return A;
}
// EXPORTS //
module.exports = gswapColumns;
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