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* @license Apache-2.0
*
* Copyright (c) 2023 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 isInteger = require( '@stdlib/assert/is-integer' ).isPrimitive;
var isCollection = require( '@stdlib/assert/is-collection' );
var isOrder = require( '@stdlib/ndarray/base/assert/is-order' );
var shape2strides = require( '@stdlib/ndarray/base/shape2strides' );
var format = require( '@stdlib/string/format' );
// MAIN //
/**
* Returns the strides of a provided ndarray.
*
* @param {ndarrayLike} x - input ndarray
* @throws {TypeError} must provide an ndarray
* @returns {IntegerArray} strides
*
* @example
* var zeros = require( '@stdlib/ndarray/zeros' );
*
* var out = strides( zeros( [ 3, 3, 3 ] ) );
* // returns [ 9, 3, 1 ]
*/
function strides( x ) {
var out;
var ord;
var sh;
var st;
var d;
var i;
// Note: we intentionally avoid rigorous ndarray checks to minimize performance impacts. This obviously means that non-ndarray-like objects can sneak through, but this is likely all right for the purposes of this function...
if ( typeof x !== 'object' || x === null ) {
throw new TypeError( format( 'invalid argument. Must provide an ndarray. Value: `%s`.', x ) );
}
st = x.strides; // TODO: consider whether we want to support ecosystem libraries, such as scijs/ndarray, which name this property `stride`
if ( !isCollection( st ) ) {
// WARNING: if no strides array, try to derive the strides from the shape. Note, however, that there is a lot that can go wrong here, as the only thing we are requiring is that the shape is a collection. The main point of going through the effort to compute strides is to support minimal ndarray-esque objects, where the only essential attributes are `shape` and `dtype` and where other attributes can be computed (e.g., `strides`, `offset`, `ndims`, `order`, etc), assuming single-segment contiguous data stored in row-major order...
sh = x.shape;
if ( !isCollection( sh ) ) {
throw new TypeError( format( 'invalid argument. Must provide an ndarray. Value: `%s`.', x ) );
}
if ( sh.length === 0 ) {
return [ 0 ];
}
ord = x.order;
if ( !isOrder( ord ) ) {
ord = 'row-major';
}
return shape2strides( sh, ord );
}
// Copy the strides in order to avoid unintended mutation...
out = [];
for ( i = 0; i < st.length; i++ ) {
d = st[ i ];
if ( !isInteger( d ) ) {
throw new TypeError( format( 'invalid argument. Must provide an ndarray. Value: `%s`.', x ) );
}
out.push( d );
}
return out;
}
// EXPORTS //
module.exports = strides;
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