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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';
// MAIN //
/**
* Generates a Toeplitz matrix using accessor arrays.
*
* @private
* @param {NonNegativeInteger} N - number of indexed elements in both `r` and `c`
* @param {Object} r - first row array object
* @param {integer} strideR - stride length for `r`
* @param {NonNegativeInteger} offsetR - starting index for `r`
* @param {Object} c - first column array object
* @param {integer} strideC - stride length for `c`
* @param {NonNegativeInteger} offsetC - starting index for `c`
* @param {Object} out - output array object
* @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 {Object} output array object
*
* @example
* var toAccessorArray = require( '@stdlib/array/base/to-accessor-array' );
* var arraylike2object = require( '@stdlib/array/base/arraylike2object' );
*
* 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, arraylike2object( toAccessorArray ( r ) ), 1, 0, arraylike2object( toAccessorArray( c ) ), 1, 0, arraylike2object( toAccessorArray( 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 rbuf;
var cbuf;
var obuf;
var getR;
var getC;
var oset;
var io;
var ij;
var i;
var j;
rbuf = r.data;
cbuf = c.data;
obuf = out.data;
getR = r.accessors[ 0 ];
getC = c.accessors[ 0 ];
oset = out.accessors[ 1 ];
io = offsetOut;
for ( i = 0; i < N; i++ ) {
ij = io;
for ( j = 0; j < N; j++ ) {
if ( j > i ) {
oset( obuf, ij, getR( rbuf, offsetR + ( ( j - i ) * strideR ) ) );
} else {
oset( obuf, ij, getC( cbuf, offsetC + ( ( i - j ) * strideC ) ) );
}
ij += strideOut2;
}
io += strideOut1;
}
return out;
}
// EXPORTS //
module.exports = gtoeplitz;
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