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* @license Apache-2.0
*
* Copyright (c) 2024 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 isArrayLikeObject = require( '@stdlib/assert/is-array-like-object' );
var isPositiveInteger = require( '@stdlib/assert/is-positive-integer' ).isPrimitive;
var iteratorSymbol = require( '@stdlib/symbol/iterator' );
var zeros = require( '@stdlib/array/base/zeros' );
var getShape = require( '@stdlib/ndarray/shape' );
var numel = require( '@stdlib/ndarray/base/numel' );
var ndslice = require( '@stdlib/ndarray/base/slice' );
var maybeBroadcastArrays = require( '@stdlib/ndarray/maybe-broadcast-arrays' );
var nextCartesianIndex = require( '@stdlib/ndarray/base/next-cartesian-index' ).assign;
var args2multislice = require( '@stdlib/slice/base/args2multislice' );
var format = require( '@stdlib/string/format' );
// MAIN //
/**
* Returns an iterator which iterates over interleaved subarrays.
*
* @param {ArrayLikeObject<ndarray>} arrays - input ndarrays
* @param {PositiveInteger} ndims - number of dimensions to stack after broadcasting
* @throws {TypeError} first argument must be an array of ndarrays
* @throws {TypeError} each ndarray after broadcasting must have at least `ndims+1` dimensions
* @throws {TypeError} second argument must be a positive integer
* @throws {Error} input ndarrays must be broadcast-compatible
* @returns {Iterator} iterator
*
* @example
* var array = require( '@stdlib/ndarray/array' );
* var ndarray2array = require( '@stdlib/ndarray/to-array' );
*
* var x = array( [ [ [ 1, 2 ], [ 3, 4 ] ], [ [ 5, 6 ], [ 7, 8 ] ] ] );
* // returns <ndarray>
*
* var iter = nditerInterleaveSubarrays( [ x, x ], 2 );
*
* var v = iter.next().value;
* // returns <ndarray>
*
* var arr = ndarray2array( v );
* // returns [ [ 1, 2 ], [ 3, 4 ] ]
*
* v = iter.next().value;
* // returns <ndarray>
*
* arr = ndarray2array( v );
* // returns [ [ 1, 2 ], [ 3, 4 ] ]
*
* // ...
*/
function nditerInterleaveSubarrays( arrays, ndims ) {
var shape;
var iter;
var list;
var FLG;
var idx;
var dim;
var tmp;
var S;
var M;
var N;
var K;
var i;
var j;
var k;
if ( !isArrayLikeObject( arrays ) ) {
throw new TypeError( format( 'invalid argument. First argument must be an array of ndarrays. Value: `%s`.', arrays ) );
}
if ( !isPositiveInteger( ndims ) ) {
throw new TypeError( format( 'invalid argument. Second argument must be a positive integer. Value: `%s`.', ndims ) );
}
// Attempt to broadcast the input ndarrays...
try {
list = maybeBroadcastArrays( arrays );
} catch ( err ) { // eslint-disable-line no-unused-vars
throw new TypeError( format( 'invalid argument. First argument must be an array of ndarrays which are broadcast-compatible. Value: `%s`.', arrays ) );
}
K = list.length;
// Retrieve input array meta data:
shape = getShape( list[ 0 ] );
M = shape.length;
// Ensure that each broadcasted input array has sufficient dimensions...
if ( M <= ndims ) {
throw new TypeError( format( 'invalid argument. First argument must be an array of ndarrays having at least %d dimensions after broadcasting.', ndims+1 ) );
}
// Check whether the broadcasted shape is empty...
N = numel( shape );
if ( N === 0 ) {
FLG = true;
}
// Compute the number of subarrays across all stacks of subarrays:
dim = M - ndims - 1;
for ( i = dim+1; i < M; i++ ) {
N /= shape[ i ];
}
N *= K;
S = shape[ dim ];
// Initialize index arrays for generating slices...
idx = [];
for ( i = 0; i < K; i++ ) {
tmp = zeros( M );
// Set the last `ndims` elements to `null` to indicate that we want a full "slice" for the last `ndims` dimensions:
for ( j = dim+1; j < M; j++ ) {
tmp[ j ] = null;
}
idx.push( tmp );
}
// Initialize counters:
i = -1;
k = -1;
// 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() {
var ibuf;
var s;
var j;
i += 1;
if ( FLG || i >= N ) {
return {
'done': true
};
}
k = ( k+1 ) % K;
ibuf = idx[ k ];
// Create a multi-slice for the current view:
s = args2multislice( ibuf );
// Update the index array:
j = ( ibuf[ dim ] + 1 ) % S;
ibuf[ dim ] = j;
if ( j === 0 ) {
// If we've iterated over all the subarrays in the current stack, move on to the next set of subarrays:
ibuf = nextCartesianIndex( shape, 'row-major', ibuf, dim-1, ibuf );
}
// Return the next slice:
return {
'value': ndslice( list[ k ], s, true, false ),
'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 nditerInterleaveSubarrays( arrays, ndims );
}
}
// EXPORTS //
module.exports = nditerInterleaveSubarrays;
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