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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-len */
'use strict';
// MODULES //
var isLayout = require( '@stdlib/blas/base/assert/is-layout' );
var isColumnMajor = require( '@stdlib/ndarray/base/assert/is-column-major-string' );
var resolveOrder = require( '@stdlib/blas/base/layout-resolve-enum' );
var binomcoef = require( '@stdlib/math/base/special/binomcoef' );
var max = require( '@stdlib/math/base/special/fast/max' );
var format = require( '@stdlib/string/format' );
var addon = require( './../src/addon.node' );
// MAIN //
/**
* Computes combinations of a specified length from double-precision floating-point strided array elements.
*
* @param {string} order - storage layout
* @param {NonNegativeInteger} N - number of indexed elements
* @param {NonNegativeInteger} k - number of elements to combine
* @param {boolean} replacement - boolean indicating whether to allow duplication in combination
* @param {Float64Array} x - input array
* @param {integer} strideX - stride length for `x`
* @param {Float64Array} out - output array
* @param {integer} LDO - stride length between successive contiguous vectors of the matrix `out` (a.k.a., leading dimension of `out`)
* @param {Int32Array} workspace - workspace array
* @param {integer} strideW - stride length for `workspace`
* @throws {TypeError} first argument must be a valid order
* @throws {RangeError} eighth argument must be a valid stride length
* @returns {Float64Array} output array
*
* @example
* var Float64Array = require( '@stdlib/array/float64' );
* var Int32Array = require( '@stdlib/array/int32' );
*
* var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0 ] );
* var out = new Float64Array( 12 );
* var workspace = new Int32Array( 2 );
*
* dcombinations( 'row-major', 4, 2, false, x, 1, out, 2, workspace, 1 );
* // out => <Float64Array>[ 1.0, 2.0, 1.0, 3.0, 1.0, 4.0, 2.0, 3.0, 2.0, 4.0, 3.0, 4.0 ]
*/
function dcombinations( order, N, k, replacement, x, strideX, out, LDO, workspace, strideW ) {
var C;
if ( !isLayout( order ) ) {
throw new TypeError( format( 'invalid argument. First argument must be a valid order. Value: `%s`.', order ) );
}
if ( isColumnMajor( order ) ) {
// For column-major order, the leading dimension is the stride between successive combinations (i.e., the columns of the output matrix), and, thus, must be large enough to avoid overlapping combinations...
if ( replacement ) {
C = binomcoef( N + k - 1, k );
} else {
C = binomcoef( N, k );
}
if ( LDO < max( 1, C ) ) {
throw new RangeError( format( 'invalid argument. Eighth argument must be greater than or equal to max(1,%d). Value: `%d`.', C, LDO ) );
}
} else if ( LDO < max( 1, k ) ) { // order === 'row-major'
throw new RangeError( format( 'invalid argument. Eighth argument must be greater than or equal to max(1,%d). Value: `%d`.', k, LDO ) );
}
if ( N <= 0 || k <= 0 ) {
return out;
}
if ( !replacement && k > N ) {
return out;
}
addon( resolveOrder( order ), N, k, replacement, x, strideX, out, LDO, workspace, strideW );
return out;
}
// EXPORTS //
module.exports = dcombinations;
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