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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 isInteger = require( '@stdlib/assert/is-integer' ).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 nulls = require( '@stdlib/array/base/nulls' );
var getShape = require( '@stdlib/ndarray/shape' );
var normalizeIndex = require( '@stdlib/ndarray/base/normalize-index' );
var numel = require( '@stdlib/ndarray/base/numel' );
var ndslice = require( '@stdlib/ndarray/base/slice' );
var Slice = require( '@stdlib/slice/ctor' );
var args2multislice = require( '@stdlib/slice/base/args2multislice' );
var format = require( '@stdlib/string/format' );
// MAIN //
/**
* Returns an iterator which iterates over each view along a specified dimension.
*
* @param {ndarray} x - input value
* @param {integer} dim - dimension index
* @param {Options} [options] - function options
* @param {boolean} [options.readonly=true] - boolean indicating whether returned views should be read-only
* @param {boolean} [options.keepdim=false] - boolean indicating whether returned views should include the selected dimension as a singleton dimension
* @throws {TypeError} first argument must be an ndarray
* @throws {TypeError} second argument must be an integer
* @throws {RangeError} dimension index exceeds the number of 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 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 = nditerSelectDimension( x, 0 );
*
* 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 nditerSelectDimension( x, dim ) {
var options;
var shape;
var ndims;
var opts;
var iter;
var FLG;
var idx;
var N;
var d;
var i;
if ( !isndarrayLike( x ) ) {
throw new TypeError( format( 'invalid argument. First argument must be an ndarray. Value: `%s`.', x ) );
}
if ( !isInteger( dim ) ) {
throw new TypeError( format( 'invalid argument. Second argument must be an integer. Value: `%s`.', dim ) );
}
opts = {
'writable': false,
'keepdim': 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.' ) );
}
}
if ( hasOwnProp( options, 'keepdim' ) ) {
if ( !isBoolean( options.keepdim ) ) {
throw new TypeError( format( 'invalid option. `%s` option must be a boolean. Option: `%s`.', 'keepdim', options.keepdim ) );
}
opts.keepdim = options.keepdim;
}
}
// Retrieve input array meta data:
shape = getShape( x );
ndims = shape.length;
// Normalize the dimension index:
d = normalizeIndex( dim, 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, dim ) );
}
// Check whether the input array is empty...
N = numel( shape );
if ( N === 0 ) {
FLG = true;
}
// Compute the number of views (i.e., the dimension size):
N = shape[ d ];
// Initialize a counter:
i = -1;
// Initialize an index array for generating slices:
idx = nulls( 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() {
var s;
i += 1;
if ( FLG || i >= N ) {
return {
'done': true
};
}
// Update the index array to generate the next view:
if ( opts.keepdim ) {
idx[ d ] = new Slice( i, i+1, 1 );
} else {
idx[ d ] = i;
}
// Create a multi-slice for the next view:
s = args2multislice( idx );
// Return the next slice:
return {
'value': ndslice( 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 nditerSelectDimension( x, dim, opts );
}
}
// EXPORTS //
module.exports = nditerSelectDimension;
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