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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 isPlainObject = require( '@stdlib/assert/is-plain-object' );
var isBoolean = require( '@stdlib/assert/is-boolean' ).isPrimitive;
var isIntegerArray = require( '@stdlib/assert/is-integer-array' ).primitives;
var isndarrayLike = require( '@stdlib/assert/is-ndarray-like' );
var isReadOnly = require( '@stdlib/ndarray/base/assert/is-read-only' );
var hasOwnProp = require( '@stdlib/assert/has-own-property' );
var iteratorSymbol = require( '@stdlib/symbol/iterator' );
var zeros = require( '@stdlib/array/base/zeros' );
var copy = require( '@stdlib/array/base/copy' );
var take = require( '@stdlib/array/base/take' );
var put = require( '@stdlib/array/base/put' );
var getShape = require( '@stdlib/ndarray/shape' );
var normalizeIndex = require( '@stdlib/ndarray/base/normalize-index' );
var numel = require( '@stdlib/ndarray/base/numel' );
var slice = require( '@stdlib/ndarray/base/slice' );
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 each subarray in a stack of subarrays according to a list of specified stack dimensions.
*
* @param {ndarray} x - input value
* @param {IntegerArray} dims - indices of dimensions to stack
* @param {Options} [options] - function options
* @param {boolean} [options.readonly=true] - boolean indicating whether returned views should be read-only
* @throws {TypeError} first argument must be an ndarray
* @throws {TypeError} first argument must have at least `dims.length+1` dimensions
* @throws {TypeError} second argument must be an array of integers
* @throws {RangeError} dimension index exceeds the number of dimensions
* @throws {Error} dimension indices must be sorted in ascending order
* @throws {Error} dimension indices must be unique
* @throws {TypeError} options argument must be an object
* @throws {TypeError} must provide valid options
* @throws {Error} cannot write to a read-only array
* @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 = nditerStacks( x, [ 1, 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 [ [ 5, 6 ], [ 7, 8 ] ]
*
* // ...
*/
function nditerStacks( x, dims ) {
var indices;
var options;
var shape;
var ndims;
var odims;
var opts;
var iter;
var ibuf;
var FLG;
var idx;
var sh;
var M;
var N;
var d;
var i;
var j;
if ( !isndarrayLike( x ) ) {
throw new TypeError( format( 'invalid argument. First argument must be an ndarray. Value: `%s`.', x ) );
}
if ( !isIntegerArray( dims ) ) {
throw new TypeError( format( 'invalid argument. Second argument must be an array of integers. Value: `%s`.', dims ) );
}
opts = {
'writable': false
};
if ( arguments.length > 2 ) {
options = arguments[ 2 ];
if ( !isPlainObject( options ) ) {
throw new TypeError( format( 'invalid argument. Options argument must be an object. Value: `%s`.', options ) );
}
if ( hasOwnProp( options, 'readonly' ) ) {
if ( !isBoolean( options.readonly ) ) {
throw new TypeError( format( 'invalid option. `%s` option must be a boolean. Option: `%s`.', 'readonly', options.readonly ) );
}
opts.writable = !options.readonly;
if ( opts.writable && isReadOnly( x ) ) {
throw new Error( format( 'invalid option. Cannot write to read-only array.' ) );
}
}
}
odims = dims; // cache a reference to the original input array
dims = copy( dims );
M = dims.length;
// Retrieve input array meta data:
shape = getShape( x );
ndims = shape.length;
// Ensure that the input array has sufficient dimensions...
if ( ndims <= M ) {
throw new TypeError( format( 'invalid argument. First argument must be an ndarray having at least %d dimensions.', M+1 ) );
}
// Normalize dimension indices...
for ( i = 0; i < M; i++ ) {
d = normalizeIndex( dims[ i ], ndims-1 );
if ( d === -1 ) {
throw new RangeError( format( 'invalid argument. Dimension index exceeds the number of dimensions. Number of dimensions: %d. Value: `%d`.', ndims, dims[ i ] ) );
}
dims[ i ] = d;
}
// Check whether the input array is empty:
N = numel( shape );
if ( N === 0 ) {
FLG = true;
}
// Ensure the indices are sorted in ascending order:
for ( i = 0; i < M-1; i++ ) {
if ( dims[ i ] > dims[ i+1 ] ) {
throw new Error( format( 'invalid argument. Dimension indices must be sorted in ascending order. Value: `%s`.', odims ) );
}
}
// Ensure that indices are unique...
j = 1;
for ( i = 1; i < M; i++ ) {
if ( dims[ i ] === dims[ i-1 ] ) {
throw new Error( format( 'invalid argument. Dimension indices must be unique. Value: `%s`.', odims ) );
}
dims[ j ] = dims[ i ];
j += 1;
}
// Compute the number of subarrays across all stacks of subarrays:
for ( i = 0; i < M; i++ ) {
N /= shape[ dims[ i ] ];
}
// Initialize an index array for generating slices:
idx = zeros( ndims );
// Set the specified dimensions to `null` to indicate that we want a full "slice" for those dimensions:
for ( i = 0; i < M; i++ ) {
idx[ dims[ i ] ] = null;
}
// Create an array of indices over which we want to iterate:
indices = [];
j = 0;
for ( i = 0; i < ndims; i++ ) {
if ( i === dims[ j ] ) {
j += 1;
continue;
}
indices.push( i );
}
// Create an index buffer for generating Cartesian indices:
sh = take( shape, indices, 'throw' );
ibuf = take( idx, indices, 'throw' );
// Initialize a counter:
i = -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 s;
i += 1;
if ( FLG || i >= N ) {
return {
'done': true
};
}
// Create a multi-slice for the current view:
s = args2multislice( idx );
// Update the index buffer:
ibuf = nextCartesianIndex( sh, 'row-major', ibuf, -1, ibuf );
// Update the index array:
idx = put( idx, indices, ibuf, 'throw' );
// Return the next slice:
return {
'value': slice( x, s, true, opts.writable ),
'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 nditerStacks( x, dims, opts );
}
}
// EXPORTS //
module.exports = nditerStacks;
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