feat: add ndarray/base/unflatten-shape

lib/node_modules/@stdlib/ndarray/base/unflatten-shape/README.md

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+<!--
+
+@license Apache-2.0
+
+Copyright (c) 2026 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.
+
+-->
+
+# unflattenShape
+
+> Expand a dimension over multiple dimensions.
+
+<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->
+
+<section class="intro">
+
+</section>
+
+<!-- /.intro -->
+
+<!-- Package usage documentation. -->
+
+<section class="usage">
+
+## Usage
+
+```javascript
+var unflattenShape = require( '@stdlib/ndarray/base/unflatten-shape' );
+```
+
+#### unflattenShape( shape, dim, sizes )
+
+Expands a dimension over multiple dimensions.
+
+```javascript
+var sh = unflattenShape( [ 6, 2, 1 ], 0, [ 3, 2 ] );
+// returns [ 3, 2, 2, 1 ]
+```
+
+The function accepts the following parameters:
+
+-   **shape**: array shape.
+-   **dim**: dimension to be unflattened. If provided an integer less than zero, the dimension index is resolved relative to the last dimension, with the last dimension corresponding to the value `-1`.
+-   **sizes**: new shape of the unflattened dimension.
+
+#### unflattenShape.assign( shape, dim, sizes, out )
+
+Expands a dimension over multiple dimensions and assigns results to a provided output array.
+
+```javascript
+var o = [ 0, 0, 0, 0 ];
+
+var out = unflattenShape.assign( [ 6, 2, 1 ], 0, [ 3, 2 ], o );
+// returns [ 3, 2, 2, 1 ]
+
+var bool = ( out === o );
+// returns true
+```
+
+The function accepts the following parameters:
+
+-   **shape**: array shape.
+-   **dim**: dimension to be unflattened. If provided an integer less than zero, the dimension index is resolved relative to the last dimension, with the last dimension corresponding to the value `-1`.
+-   **sizes**: new shape of the unflattened dimension.
+-   **out**: output array.
+
+</section>
+
+<!-- /.usage -->
+
+<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
+
+<section class="notes">
+
+</section>
+
+<!-- /.notes -->
+
+<!-- Package usage examples. -->
+
+<section class="examples">
+
+## Examples
+
+<!-- eslint no-undef: "error" -->
+
+```javascript
+var unflattenShape = require( '@stdlib/ndarray/base/unflatten-shape' );
+
+var out = unflattenShape( [ 2, 4, 1 ], 1, [ 2, 2 ] );
+// returns [ 2, 2, 2, 1 ]
+
+out = unflattenShape( [ 2, 4, 1 ], 1, [ 2, 1, 2 ] );
+// returns [ 2, 2, 1, 2, 1 ]
+
+out = unflattenShape( [ 2, 4, 1 ], 1, [ 2, 1, 1, 2 ] );
+// returns [ 2, 2, 1, 1, 2, 1 ]
+```
+
+</section>
+
+<!-- /.examples -->
+
+<!-- Section to include cited references. If references are included, add a horizontal rule *before* the section. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
+
+<section class="references">
+
+</section>
+
+<!-- /.references -->
+
+<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->
+
+<section class="related">
+
+</section>
+
+<!-- /.related -->
+
+<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
+
+<section class="links">
+
+</section>
+
+<!-- /.links -->

lib/node_modules/@stdlib/ndarray/base/unflatten-shape/benchmark/benchmark.js

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+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2026 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 bench = require( '@stdlib/bench' );
+var isArray = require( '@stdlib/assert/is-array' );
+var format = require( '@stdlib/string/format' );
+var pkg = require( './../package.json' ).name;
+var unflattenShape = require( './../lib' );
+
+
+// MAIN //
+
+bench( pkg, function benchmark( b ) {
+	var shape;
+	var sizes;
+	var out;
+	var i;
+
+	shape = [ 5, 9, 3, 4, 2 ];
+	sizes = [ 1, 1, 3 ];
+
+	b.tic();
+	for ( i = 0; i < b.iterations; i++ ) {
+		out = unflattenShape( shape, 2, sizes );
+		if ( out.length !== 7 ) {
+			b.fail( 'should have expected length' );
+		}
+	}
+	b.toc();
+	if ( !isArray( out ) ) {
+		b.fail( 'should return an array' );
+	}
+	b.pass( 'benchmark finished' );
+	b.end();
+});
+
+bench( format( '%s:assign', pkg ), function benchmark( b ) {
+	var shape;
+	var sizes;
+	var out;
+	var i;
+
+	shape = [ 5, 9, 3, 4, 2 ];
+	sizes = [ 1, 1, 3 ];
+	out = [ 0, 0, 0, 0, 0, 0, 0 ];
+
+	b.tic();
+	for ( i = 0; i < b.iterations; i++ ) {
+		out = unflattenShape.assign( shape, 2, sizes, out );
+		if ( out.length !== 7 ) {
+			b.fail( 'should have expected length' );
+		}
+	}
+	b.toc();
+	if ( !isArray( out ) ) {
+		b.fail( 'should return an array' );
+	}
+	b.pass( 'benchmark finished' );
+	b.end();
+});

lib/node_modules/@stdlib/ndarray/base/unflatten-shape/docs/repl.txt

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+
+{{alias}}( shape, dim, sizes )
+    Expands a dimension over multiple dimensions.
+
+    Parameters
+    ----------
+    shape: ArrayLike<number>
+        Array shape.
+
+    dim: integer
+        Dimension to be unflattened. If less than zero, the index is resolved
+        relative to the last dimension, with the last dimension corresponding to
+        the value `-1`.
+
+    sizes: ArrayLike<number>
+        New shape of the unflattened dimension.
+
+    Returns
+    -------
+    out: Array<number>
+        Unflattened shape.
+
+    Examples
+    --------
+    > var sh = [ 6, 2, 1 ];
+    > var sizes = [ 3, 2 ];
+    > var out = {{alias}}( sh, 0, sizes )
+    [ 3, 2, 2, 1 ]
+
+
+{{alias}}.assign( shape, dim, sizes, out )
+    Expands a dimension over multiple dimensions and assigns results to a
+    provided output array.
+
+    Parameters
+    ----------
+    shape: ArrayLike<number>
+        Array shape.
+
+    dim: integer
+        Dimension to be unflattened. If less than zero, the index is resolved
+        relative to the last dimension, with the last dimension corresponding to
+        the value `-1`.
+
+    sizes: ArrayLike<number>
+        New shape of the unflattened dimension.
+
+    out: Array|TypedArray|Object
+        Output array.
+
+    Returns
+    -------
+    out: Array|TypedArray|Object
+        Output array.
+
+    Examples
+    --------
+    > var sh = [ 6, 2, 1 ];
+    > var sizes = [ 3, 2 ];
+    > var o = [ 0, 0, 0, 0 ];
+    > var out = {{alias}}.assign( sh, 0, sizes, o )
+    [ 3, 2, 2, 1 ]
+    > var bool = ( o === out )
+    true
+
+    See Also
+    --------

lib/node_modules/@stdlib/ndarray/base/unflatten-shape/docs/types/index.d.ts

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+/*
+* @license Apache-2.0
+*
+* Copyright (c) 2026 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.
+*/
+
+// TypeScript Version: 4.1
+
+/// <reference types="@stdlib/types"/>
+
+import { ArrayLike } from '@stdlib/types/array';
+
+/**
+* Interface describing `unflattenShape`.
+*/
+interface Routine {
+	/**
+	* Expands a dimension over multiple dimensions.
+	*
+	* @param shape - array shape
+	* @param dim - dimension to be unflattened
+	* @param sizes - new shape of the unflattened dimension
+	* @returns unflattened shape
+	*
+	* @example
+	* var sh = unflattenShape( [ 6, 2, 1 ], 0, [ 3, 2 ] );
+	* // returns [ 3, 2, 2, 1 ]
+	*/
+	( shape: ArrayLike<number>, dim: number, sizes: ArrayLike<number> ): Array<number>;
+
+	/**
+	* Expands a dimension over multiple dimensions.
+	*
+	* @param shape - array shape
+	* @param dim - dimension to be unflattened
+	* @param sizes - new shape of the unflattened dimension
+	* @param out - output array
+	* @returns unflattened shape
+	*
+	* @example
+	* var o = [ 0, 0, 0, 0 ];
+	*
+	* var out = unflattenShape.assign( [ 6, 2, 1 ], 0, [ 3, 2 ], o );
+	* // returns [ 3, 2, 2, 1 ]
+	*
+	* var bool = ( out === o );
+	* // returns true
+	*/
+	assign<T extends ArrayLike<number> = ArrayLike<number>>( shape: ArrayLike<number>, dim: number, sizes: ArrayLike<number>, out: T ): T;
+}
+
+/**
+* Expands a dimension over multiple dimensions.
+*
+* @param shape - array shape
+* @param dim - dimension to be unflattened
+* @param sizes - new shape of the unflattened dimension
+* @returns unflattened shape
+*
+* @example
+* var sh = unflattenShape( [ 6, 2, 1 ], 0, [ 3, 2 ] );
+* // returns [ 3, 2, 2, 1 ]
+*
+* @example
+* var o = [ 0, 0, 0, 0 ];
+*
+* var out = unflattenShape.assign( [ 6, 2, 1 ], 0, [ 3, 2 ], o );
+* // returns [ 3, 2, 2, 1 ]
+*
+* var bool = ( out === o );
+* // returns true
+*/
+declare var unflattenShape: Routine;
+
+
+// EXPORTS //
+
+export = unflattenShape;