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Commit 534fbd0

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headlessNodekgryte
andauthored
feat: add ndarray/base/shift
PR-URL: #8118 Ref: #2656 Closes: stdlib-js/metr-issue-tracker#87 Co-authored-by: Athan Reines <kgryte@gmail.com> Reviewed-by: Athan Reines <kgryte@gmail.com>
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<!--
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@license Apache-2.0
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Copyright (c) 2025 The Stdlib Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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# shift
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> Return an array containing a truncated view of an input ndarray and a view of the first element(s) along a specified dimension.
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<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->
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<section class="intro">
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</section>
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<!-- /.intro -->
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<!-- Package usage documentation. -->
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<section class="usage">
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## Usage
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```javascript
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var shift = require( '@stdlib/ndarray/base/shift' );
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```
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#### shift( x, dim, writable )
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Returns an array containing a truncated view of an input ndarray and a view of the first element(s) along a specified dimension.
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```javascript
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var ndarray = require( '@stdlib/ndarray/ctor' );
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var getShape = require( '@stdlib/ndarray/shape' );
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var ndarray2array = require( '@stdlib/ndarray/to-array' );
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var buffer = [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ];
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var shape = [ 3, 2 ];
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var strides = [ 2, 1 ];
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var offset = 0;
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var x = ndarray( 'generic', buffer, shape, strides, offset, 'row-major' );
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// returns <ndarray>
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var sh = getShape( x );
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// returns [ 3, 2 ]
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var arr = ndarray2array( x );
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// returns [ [ 1.0, 2.0 ], [ 3.0, 4.0 ], [ 5.0, 6.0 ] ]
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var y = shift( x, 0, false );
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// returns [ <ndarray>, <ndarray> ]
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arr = ndarray2array( y[ 0 ] );
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// returns [ [ 3.0, 4.0 ], [ 5.0, 6.0 ] ]
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arr = ndarray2array( y[ 1 ] );
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// returns [ [ 1.0, 2.0 ] ]
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```
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The function accepts the following arguments:
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- **x**: input ndarray.
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- **dim**: dimension along which to perform the operation. 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`.
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- **writable**: boolean indicating whether a returned ndarray should be writable.
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</section>
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<!-- /.usage -->
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<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="notes">
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## Notes
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- The `writable` parameter **only** applies to ndarray constructors supporting **read-only** instances.
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</section>
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<!-- /.notes -->
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<!-- Package usage examples. -->
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<section class="examples">
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## Examples
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<!-- eslint no-undef: "error" -->
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```javascript
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var array = require( '@stdlib/ndarray/array' );
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var ndarray2array = require( '@stdlib/ndarray/to-array' );
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var zeroTo = require( '@stdlib/array/base/zero-to' );
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var shift = require( '@stdlib/ndarray/base/shift' );
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// Create a linear ndarray buffer:
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var buf = zeroTo( 27 );
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// Create an ndarray which is a stack of three 3x3 matrices:
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var x = array( buf, {
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'shape': [ 3, 3, 3 ]
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});
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// Remove the first row from each matrix:
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var y = shift( x, 1, false );
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// returns [ <ndarray>, <ndarray> ]
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console.log( ndarray2array( y[ 0 ] ) );
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console.log( ndarray2array( y[ 1 ] ) );
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```
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</section>
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<!-- /.examples -->
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<!-- 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. -->
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<section class="references">
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</section>
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<!-- /.references -->
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<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->
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<section class="related">
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</section>
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<!-- /.related -->
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<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="links">
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</section>
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<!-- /.links -->
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/**
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* @license Apache-2.0
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*
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* Copyright (c) 2025 The Stdlib Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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'use strict';
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// MODULES //
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var bench = require( '@stdlib/bench' );
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var isndarrayLike = require( '@stdlib/assert/is-ndarray-like' );
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var empty = require( '@stdlib/ndarray/empty' );
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var pkg = require( './../package.json' ).name;
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var shift = require( './../lib' );
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// MAIN //
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bench( pkg+'::1d', function benchmark( b ) {
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var values;
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var v;
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var i;
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/* eslint-disable object-curly-newline, stdlib/line-closing-bracket-spacing */
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values = [
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empty( [ 2 ], { 'dtype': 'float64' } ),
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empty( [ 2 ], { 'dtype': 'float32' } ),
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empty( [ 2 ], { 'dtype': 'int32' } ),
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empty( [ 2 ], { 'dtype': 'complex128' } ),
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empty( [ 2 ], { 'dtype': 'generic' } )
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];
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/* eslint-enable object-curly-newline, stdlib/line-closing-bracket-spacing */
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b.tic();
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for ( i = 0; i < b.iterations; i++ ) {
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v = shift( values[ i%values.length ], 0, false );
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if ( typeof v !== 'object' ) {
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b.fail( 'should return an array of ndarrays' );
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}
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}
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b.toc();
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if ( !isndarrayLike( v[0] ) || !isndarrayLike( v[1] ) ) {
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b.fail( 'should return an array of ndarrays' );
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}
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b.pass( 'benchmark finished' );
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b.end();
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});
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bench( pkg+'::2d', function benchmark( b ) {
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var values;
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var v;
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var i;
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/* eslint-disable object-curly-newline, stdlib/line-closing-bracket-spacing */
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values = [
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empty( [ 2, 2 ], { 'dtype': 'float64' } ),
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empty( [ 2, 2 ], { 'dtype': 'float32' } ),
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empty( [ 2, 2 ], { 'dtype': 'int32' } ),
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empty( [ 2, 2 ], { 'dtype': 'complex128' } ),
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empty( [ 2, 2 ], { 'dtype': 'generic' } )
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];
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/* eslint-enable object-curly-newline, stdlib/line-closing-bracket-spacing */
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b.tic();
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for ( i = 0; i < b.iterations; i++ ) {
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v = shift( values[ i%values.length ], 0, false );
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if ( typeof v !== 'object' ) {
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b.fail( 'should return an array of ndarrays' );
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}
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}
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b.toc();
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if ( !isndarrayLike( v[0] ) || !isndarrayLike( v[1] ) ) {
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b.fail( 'should return an array of ndarrays' );
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}
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b.pass( 'benchmark finished' );
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b.end();
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});
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bench( pkg+'::3d', function benchmark( b ) {
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var values;
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var v;
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var i;
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/* eslint-disable object-curly-newline, stdlib/line-closing-bracket-spacing */
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values = [
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empty( [ 2, 2, 2 ], { 'dtype': 'float64' } ),
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empty( [ 2, 2, 2 ], { 'dtype': 'float32' } ),
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empty( [ 2, 2, 2 ], { 'dtype': 'int32' } ),
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empty( [ 2, 2, 2 ], { 'dtype': 'complex128' } ),
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empty( [ 2, 2, 2 ], { 'dtype': 'generic' } )
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];
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/* eslint-enable object-curly-newline, stdlib/line-closing-bracket-spacing */
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b.tic();
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for ( i = 0; i < b.iterations; i++ ) {
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v = shift( values[ i%values.length ], 0, false );
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if ( typeof v !== 'object' ) {
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b.fail( 'should return an array of ndarrays' );
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}
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}
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b.toc();
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if ( !isndarrayLike( v[0] ) || !isndarrayLike( v[1] ) ) {
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b.fail( 'should return an array of ndarrays' );
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}
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b.pass( 'benchmark finished' );
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b.end();
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});
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bench( pkg+'::4d', function benchmark( b ) {
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var values;
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var v;
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var i;
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/* eslint-disable object-curly-newline, stdlib/line-closing-bracket-spacing */
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values = [
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empty( [ 2, 2, 2, 2 ], { 'dtype': 'float64' } ),
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empty( [ 2, 2, 2, 2 ], { 'dtype': 'float32' } ),
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empty( [ 2, 2, 2, 2 ], { 'dtype': 'int32' } ),
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empty( [ 2, 2, 2, 2 ], { 'dtype': 'complex128' } ),
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empty( [ 2, 2, 2, 2 ], { 'dtype': 'generic' } )
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];
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/* eslint-enable object-curly-newline, stdlib/line-closing-bracket-spacing */
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b.tic();
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for ( i = 0; i < b.iterations; i++ ) {
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v = shift( values[ i%values.length ], 0, false );
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if ( typeof v !== 'object' ) {
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b.fail( 'should return an array of ndarrays' );
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}
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}
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b.toc();
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if ( !isndarrayLike( v[0] ) || !isndarrayLike( v[1] ) ) {
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b.fail( 'should return an array of ndarrays' );
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}
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b.pass( 'benchmark finished' );
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b.end();
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});
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bench( pkg+'::5d', function benchmark( b ) {
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var values;
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var v;
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var i;
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/* eslint-disable object-curly-newline, stdlib/line-closing-bracket-spacing */
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values = [
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empty( [ 2, 2, 2, 2, 2 ], { 'dtype': 'float64' } ),
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empty( [ 2, 2, 2, 2, 2 ], { 'dtype': 'float32' } ),
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empty( [ 2, 2, 2, 2, 2 ], { 'dtype': 'int32' } ),
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empty( [ 2, 2, 2, 2, 2 ], { 'dtype': 'complex128' } ),
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empty( [ 2, 2, 2, 2, 2 ], { 'dtype': 'generic' } )
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];
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/* eslint-enable object-curly-newline, stdlib/line-closing-bracket-spacing */
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b.tic();
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for ( i = 0; i < b.iterations; i++ ) {
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v = shift( values[ i%values.length ], 0, false );
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if ( typeof v !== 'object' ) {
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b.fail( 'should return an array of ndarrays' );
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}
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}
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b.toc();
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if ( !isndarrayLike( v[0] ) || !isndarrayLike( v[1] ) ) {
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b.fail( 'should return an array of ndarrays' );
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}
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b.pass( 'benchmark finished' );
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b.end();
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});
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{{alias}}( x, dim, writable )
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Returns an array containing a truncated view of an input ndarray and a view
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of the first element(s) along a specified dimension.
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Parameters
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----------
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x: ndarray
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Input array.
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dim: integer
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Dimension along which to perform the operation. If provided an integer
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less than zero, the dimension index is resolved relative to the last
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dimension, with the last dimension corresponding to the value `-1`.
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writable: boolean
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Boolean indicating whether a returned ndarray should be writable. This
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parameter only applies to ndarray constructors which support read-only
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instances.
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Returns
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-------
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out: Array<ndarray>
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An array containing a truncated view of an input ndarray and a view of
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the first element(s) along a specified dimension.
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Examples
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--------
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> var x = {{alias:@stdlib/ndarray/array}}( [ [ 1, 2 ], [ 3, 4 ] ] )
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<ndarray>
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> var y = {{alias}}( x, 1, false )
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[ <ndarray>, <ndarray> ]
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> {{alias:@stdlib/ndarray/to-array}}( y[0] )
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[ [ 2 ], [ 4 ] ]
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> {{alias:@stdlib/ndarray/to-array}}( y[1] )
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[ [ 1 ], [ 3 ] ]
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See Also
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--------

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