@stdlib/ndarray-iter-matrix-entries
Version:
Create an iterator which returns [index, matrix] pairs for each matrix in a stack of matrices.
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JavaScript
/**
* @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.
*/
;
// 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 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 getShape = require( '@stdlib/ndarray-shape' );
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 returns `[index, matrix]` pairs for each matrix in a stack of matrices.
*
* @param {ndarray} x - input array
* @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 three dimensions
* @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 ndarray2array = require( '@stdlib/ndarray-to-array' );
* var array = require( '@stdlib/ndarray-array' );
*
* var x = array( [ [ [ 1, 2 ], [ 3, 4 ] ], [ [ 5, 6 ], [ 7, 8 ] ] ] );
* // returns <ndarray>
*
* var iter = nditerMatrixEntries( x );
*
* var v = iter.next().value;
* // returns [...]
*
* var idx = v[ 0 ];
* // returns [ 0, null, null ]
*
* var mat = ndarray2array( v[ 1 ] );
* // returns [ [ 1, 2 ], [ 3, 4 ] ]
*
* v = iter.next().value;
* // returns [...]
*
* idx = v[ 0 ];
* // returns [ 1, null, null ]
*
* mat = ndarray2array( v[ 1 ] );
* // returns [ [ 5, 6 ], [ 7, 8 ] ]
*
* // ...
*/
function nditerMatrixEntries( x ) {
var options;
var shape;
var ndims;
var opts;
var iter;
var FLG;
var idx;
var dim;
var S2;
var N;
var i;
if ( !isndarrayLike( x ) ) {
throw new TypeError( format( 'invalid argument. First argument must be an ndarray. Value: `%s`.', x ) );
}
opts = {
'writable': false
};
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, '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.' ) );
}
}
}
// Retrieve input array meta data:
shape = getShape( x );
ndims = shape.length;
// Ensure that the input array has sufficient dimensions...
if ( ndims < 3 ) {
throw new TypeError( 'invalid argument. First argument must be an ndarray having at least three dimensions.' );
}
// Check whether the input array is empty...
N = numel( shape );
if ( N === 0 ) {
FLG = true;
}
// Compute the number of matrices across all stacks of matrices:
N /= shape[ ndims-1 ] * shape[ ndims-2 ];
dim = ndims - 3;
S2 = shape[ dim ];
// Initialize a counter:
i = -1;
// Initialize an index array:
idx = zeros( ndims );
// Set the last two elements to `null` to indicate that we want a full "slice" for the last two dimensions:
idx[ ndims-1 ] = null;
idx[ ndims-2 ] = null;
// 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 indices;
var s;
var j;
i += 1;
if ( FLG || i >= N ) {
return {
'done': true
};
}
// Cache the current state of the index array:
indices = idx.slice();
// Create a multi-slice for the current view:
s = args2multislice( idx );
// Update the index array:
j = ( idx[ dim ] + 1 ) % S2;
idx[ dim ] = j;
if ( j === 0 ) {
// If we've iterated over all the matrices in the current stack, move on to the next set of matrices:
idx = nextCartesianIndex( shape, 'row-major', idx, dim-1, idx );
}
// Return the next matrix entry:
return {
'value': [ indices, 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 nditerMatrixEntries( x, opts );
}
}
// EXPORTS //
module.exports = nditerMatrixEntries;