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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.
*/
/* eslint-disable max-params */
'use strict';
// MODULES //
var arraylike2object = require( '@stdlib/array/base/arraylike2object' );
var accessors = require( './accessors.js' );
// MAIN //
/**
* Generates a Toeplitz matrix using alternative indexing semantics.
*
* @param {NonNegativeInteger} N - number of indexed elements in both `r` and `c`
* @param {Collection} r - first row of the matrix
* @param {integer} strideR - stride length for `r`
* @param {NonNegativeInteger} offsetR - starting index for `r`
* @param {Collection} c - first column of the matrix
* @param {integer} strideC - stride length for `c`
* @param {NonNegativeInteger} offsetC - starting index for `c`
* @param {Collection} out - output array
* @param {integer} strideOut1 - stride length for the first dimension of `out`
* @param {integer} strideOut2 - stride length for the second dimension of `out`
* @param {NonNegativeInteger} offsetOut - starting index for `out`
* @returns {Collection} output matrix
*
* @example
* var r = [ 1.0, 2.0, 3.0 ];
* var c = [ 1.0, 4.0, 5.0 ];
* var out = [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ];
*
* gtoeplitz( 3, r, 1, 0, c, 1, 0, out, 3, 1, 0 );
* // out => [ 1.0, 2.0, 3.0, 4.0, 1.0, 2.0, 5.0, 4.0, 1.0 ]
*/
function gtoeplitz( N, r, strideR, offsetR, c, strideC, offsetC, out, strideOut1, strideOut2, offsetOut ) { // eslint-disable-line max-len
var ro;
var co;
var oo;
var io;
var ij;
var i;
var j;
if ( N <= 0 ) {
return out;
}
ro = arraylike2object( r );
co = arraylike2object( c );
oo = arraylike2object( out );
if ( ro.accessorProtocol || co.accessorProtocol || oo.accessorProtocol ) {
accessors( N, ro, strideR, offsetR, co, strideC, offsetC, oo, strideOut1, strideOut2, offsetOut ); // eslint-disable-line max-len
return out;
}
io = offsetOut;
for ( i = 0; i < N; i++ ) {
ij = io;
for ( j = 0; j < N; j++ ) {
if ( j > i ) {
out[ ij ] = r[ offsetR + ( ( j - i ) * strideR ) ];
} else {
out[ ij ] = c[ offsetC + ( ( i - j ) * strideC ) ];
}
ij += strideOut2;
}
io += strideOut1;
}
return out;
}
// EXPORTS //
module.exports = gtoeplitz;
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