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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 setReadOnly = require( '@stdlib/utils/define-nonenumerable-read-only-property' );
var isPlainObject = require( '@stdlib/assert/is-plain-object' );
var isOrder = require( '@stdlib/ndarray/base/assert/is-order' );
var isRowMajor = require( '@stdlib/ndarray/base/assert/is-row-major-string' );
var isCollection = require( '@stdlib/assert/is-collection' );
var isNonNegativeInteger = require( '@stdlib/assert/is-nonnegative-integer' ).isPrimitive;
var hasOwnProp = require( '@stdlib/assert/has-own-property' );
var iteratorSymbol = require( '@stdlib/symbol/iterator' );
var zeros = require( '@stdlib/array/base/zeros' );
var numel = require( '@stdlib/ndarray/base/numel' );
var nextCartesianIndex = require( '@stdlib/ndarray/base/next-cartesian-index' ).assign;
var format = require( '@stdlib/string/format' );
// MAIN //
/**
* Returns an iterator which returns indices for use in indexing into an ndarray having a specified shape.
*
* @param {NonNegativeIntegerArray} shape - input shape
* @param {Options} [options] - function options
* @param {boolean} [options.order='row-major'] - index iteration order
* @throws {TypeError} first argument must be an array containing nonnegative integers
* @throws {TypeError} options argument must be an object
* @throws {TypeError} must provide valid options
* @returns {Iterator} iterator
*
* @example
* var array = require( '@stdlib/ndarray/array' );
*
* var x = array( [ [ [ 1, 2 ], [ 3, 4 ] ], [ [ 5, 6 ], [ 7, 8 ] ] ] );
* // returns <ndarray>
*
* var iter = nditerIndices( x.shape );
*
* var v = iter.next().value;
* // returns [ 0, 0, 0 ]
*
* v = iter.next().value;
* // returns [ 0, 0, 1 ]
*
* v = iter.next().value;
* // returns [ 0, 1, 0 ]
*
* // ...
*/
function nditerIndices( shape ) {
var options;
var ndims;
var opts;
var iter;
var FLG;
var idx;
var dim;
var sh;
var N;
var i;
if ( !isCollection( shape ) ) {
throw new TypeError( format( 'invalid argument. First argument must be an array of nonnegative integers. Value: `%s`.', shape ) );
}
opts = {
'order': 'row-major'
};
if ( arguments.length > 1 ) {
options = arguments[ 1 ];
if ( !isPlainObject( options ) ) {
throw new TypeError( format( 'invalid argument. Options argument must be an object. Value: `%s`.', options ) );
}
if ( hasOwnProp( options, 'order' ) ) {
if ( !isOrder( options.order ) ) {
throw new TypeError( format( 'invalid option. `%s` option must be a recognized order. Option: `%s`.', 'order', options.order ) );
}
opts.order = options.order;
}
}
// Retrieve the number of dimensions:
ndims = shape.length;
// Copy the input shape:
sh = [];
for ( i = 0; i < ndims; i++ ) {
if ( !isNonNegativeInteger( shape[ i ] ) ) {
throw new TypeError( format( 'invalid argument. First argument must be an array of nonnegative integers. Value: `%s`.', shape ) );
}
sh.push( shape[ i ] );
}
// Check whether the input array is empty...
N = numel( sh );
if ( N === 0 ) {
FLG = true;
}
// Resolve the dimension in which indices iterate fastest:
if ( isRowMajor( opts.order ) ) {
dim = ndims - 1;
} else {
dim = 0;
}
// Initialize a counter:
i = -1;
// Initialize an index array:
idx = zeros( ndims );
// Create an iterator protocol-compliant object:
iter = {};
setReadOnly( iter, 'next', next );
setReadOnly( iter, 'return', end );
// If an environment supports `Symbol.iterator`, make the iterator iterable:
if ( iteratorSymbol ) {
setReadOnly( iter, iteratorSymbol, factory );
}
return iter;
/**
* Returns an iterator protocol-compliant object containing the next iterated value.
*
* @private
* @returns {Object} iterator protocol-compliant object
*/
function next() {
i += 1;
if ( FLG || i >= N ) {
return {
'done': true
};
}
if ( i > 0 ) {
idx = nextCartesianIndex( sh, opts.order, idx, dim, idx );
}
// Return the next set of indices:
return {
'value': idx.slice(),
'done': false
};
}
/**
* Finishes an iterator.
*
* @private
* @param {*} [value] - value to return
* @returns {Object} iterator protocol-compliant object
*/
function end( value ) {
FLG = true;
if ( arguments.length ) {
return {
'value': value,
'done': true
};
}
return {
'done': true
};
}
/**
* Returns a new iterator.
*
* @private
* @returns {Iterator} iterator
*/
function factory() {
return nditerIndices( sh, opts );
}
}
// EXPORTS //
module.exports = nditerIndices;
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