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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';
// MODULES //
var isLayout = require( '@stdlib/blas/base/assert/is-layout' );
var isRowMajor = require( '@stdlib/ndarray/base/assert/is-row-major-string' );
var normalizeIndex = require( '@stdlib/ndarray/base/normalize-index' );
var max = require( '@stdlib/math/base/special/fast/max' );
var format = require( '@stdlib/string/format' );
var ndarray = require( './ndarray.js' );
// 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`.
*
* @param {string} order - storage layout of `A`
* @param {NonNegativeInteger} M - number of rows in matrix `A`
* @param {NonNegativeInteger} N - number of columns in matrix `A`
* @param {integer} i - index of the first column to interchange
* @param {integer} j - index of the second column to interchange
* @param {Collection} A - input matrix
* @param {PositiveInteger} LDA - stride length for the first dimension of `A` (a.k.a., leading dimension of the matrix `A`)
* @throws {TypeError} first argument must be a valid order
* @throws {RangeError} fourth argument must resolve to a valid column index
* @throws {RangeError} fifth argument must resolve to a valid column index
* @throws {RangeError} seventh argument must be greater than or equal to max(1,M) when `A` is stored in column-major order and max(1,N) when `A` is stored in row-major order
* @returns {Collection} `A`
*
* @example
* var A = [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ]; // => [ [ 1.0, 2.0 ], [ 3.0, 4.0 ], [ 5.0, 6.0 ] ]
*
* gswapColumns( 'row-major', 3, 2, 0, 1, A, 2 );
* // A => [ 2.0, 1.0, 4.0, 3.0, 6.0, 5.0 ]
*/
function gswapColumns( order, M, N, i, j, A, LDA ) {
var sa1;
var sa2;
var io;
var jo;
var s;
if ( !isLayout( order ) ) {
throw new TypeError( format( 'invalid argument. First argument must be a valid order. Value: `%s`.', order ) );
}
io = normalizeIndex( i, N-1 );
if ( io < 0 ) {
throw new RangeError( format( 'invalid argument. Fourth argument must resolve to a valid column index. Value: `%d`.', i ) );
}
jo = normalizeIndex( j, N-1 );
if ( jo < 0 ) {
throw new RangeError( format( 'invalid argument. Fifth argument must resolve to a valid column index. Value: `%d`.', j ) );
}
if ( isRowMajor( order ) ) {
s = N;
sa1 = LDA;
sa2 = 1;
} else {
s = M;
sa1 = 1;
sa2 = LDA;
}
if ( LDA < max( 1, s ) ) {
throw new RangeError( format( 'invalid argument. Seventh argument must be greater than or equal to max(1,%d). Value: `%d`.', s, LDA ) );
}
return ndarray( M, N, io, jo, A, sa1, sa2, 0 );
}
// EXPORTS //
module.exports = gswapColumns;
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