All files / prepend-singleton-dimensions/lib main.js

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/**
* @license Apache-2.0
*
* Copyright (c) 2022 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 getDType = require( '@stdlib/ndarray/base/dtype' );
var getShape = require( '@stdlib/ndarray/base/shape' );
var getStrides = require( '@stdlib/ndarray/base/strides' );
var getOffset = require( '@stdlib/ndarray/base/offset' );
var getOrder = require( '@stdlib/ndarray/base/order' );
var getData = require( '@stdlib/ndarray/base/data-buffer' );
 
 
// MAIN //
 
/**
* Returns an array with a specified number of prepended singleton dimensions.
*
* @param {ndarray} x - input array
* @param {NonNegativeInteger} n - number of singleton dimensions to prepend
* @param {boolean} writable - boolean indicating whether a returned array should be writable
* @returns {ndarray} output array
*
* @example
* var array = require( '@stdlib/ndarray/array' );
*
* var x = array( [ [ 1, 2 ], [ 3, 4 ] ] );
* // returns <ndarray>[ [ 1, 2 ], [ 3, 4 ] ]
*
* var y = prependSingletonDimensions( x, 3, false );
* // returns <ndarray>[ [ [ [ [ 1, 2 ], [ 3, 4 ] ] ] ] ]
*/
function prependSingletonDimensions( x, n, writable ) { // eslint-disable-line id-length
	var strides;
	var shape;
	var sh;
	var st;
	var N;
	var i;

	sh = getShape( x, false );
	st = getStrides( x, false );
	N = sh.length;

	strides = [];
	shape = [];

	// Prepend singleton dimensions...
	for ( i = 0; i < n; i++ ) {
		shape.push( 1 );
		strides.push( st[ 0 ] );
	}
	// Copy remaining dimensions...
	for ( i = 0; i < N; i++ ) {
		shape.push( sh[ i ] );
		strides.push( st[ i ] );
	}
	return new x.constructor( getDType( x ), getData( x ), shape, strides, getOffset( x ), getOrder( x ), { // eslint-disable-line max-len
		'readonly': !writable
	});
}
 
 
// EXPORTS //
 
module.exports = prependSingletonDimensions;