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base/at/README.md

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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.
+
+-->
+
+# at
+
+> Return an element from an array.
+
+<!-- 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 at = require( '@stdlib/array/base/at' );
+```
+
+#### at( x, index )
+
+Return an element from an array.
+
+```javascript
+var x = [ 1, 2, 3, 4 ];
+
+var out = at( x, 0 );
+// returns 1
+
+out = at( x, 1 );
+// returns 2
+
+out = at( x, -2 );
+// returns 3
+```
+
+The function accepts the following arguments:
+
+-   **x**: an input array.
+-   **index**: element index.
+
+</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">
+
+## Notes
+
+-   If provided an array-like object having an `at` method , the function defers execution to that method and assumes that the method has the following signature:
+
+    ```text
+    x.at( index )
+    ```
+
+    If provided an array-like object without an `at` method, the function normalizes a provided index and returns a specified element.
+
+-   Negative indices are resolved relative to the last array element, with the last element corresponding to `-1`.
+
+-   If provided out-of-bounds indices, the function always returns `undefined`.
+
+</section>
+
+<!-- /.notes -->
+
+<!-- Package usage examples. -->
+
+<section class="examples">
+
+## Examples
+
+<!-- eslint no-undef: "error" -->
+
+```javascript
+var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
+var at = require( '@stdlib/array/base/at' );
+
+// Define an array:
+var x = discreteUniform( 10, -100, 100 );
+
+// Define an array containing random index values:
+var indices = discreteUniform( 100, -x.length, x.length-1 );
+
+// Randomly selected values from the input array:
+var i;
+for ( i = 0; i < indices.length; i++ ) {
+    console.log( 'x[%d] = %d', indices[ i ], at( x, indices[ i ] ) );
+}
+```
+
+</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 -->

base/at/benchmark/benchmark.js

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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 bench = require( '@stdlib/bench' );
+var uniform = require( '@stdlib/random/array/uniform' );
+var isnan = require( '@stdlib/math/base/assert/is-nan' );
+var pkg = require( './../package.json' ).name;
+var at = require( './../lib' );
+
+
+// MAIN //
+
+bench( pkg, function benchmark( b ) {
+	var x;
+	var v;
+	var i;
+	var j;
+
+	x = uniform( 100, 0.0, 10.0 );
+
+	b.tic();
+	for ( i = 0; i < b.iterations; i++ ) {
+		j = ( i%20 ) - 10;
+		v = at( x, j );
+		if ( v !== v ) {
+			b.fail( 'should not return NaN' );
+		}
+	}
+	b.toc();
+	if ( isnan( v ) ) {
+		b.fail( 'should not return NaN' );
+	}
+	b.pass( 'benchmark finished' );
+	b.end();
+});

base/at/docs/repl.txt

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+
+{{alias}}( x, index )
+    Returns an element from an array.
+
+    Negative indices are resolved relative to the last array element, with the
+    last element corresponding to `-1`.
+
+    If provided an array-like object having an `at` method , the function defers
+    execution to that method and assumes that the method has the following
+    signature:
+
+      x.at( index )
+
+    If provided an array-like object without an `at` method, the function
+    normalizes a provided index and returns a specified element.
+
+    If provided an out-of-bounds index, the function always returns `undefined`.
+
+    Parameters
+    ----------
+    x: ArrayLikeObject
+        Input array.
+
+    index: integer
+        Element index.
+
+    Returns
+    -------
+    out: any
+        Element value.
+
+    Examples
+    --------
+    > var x = [ 1, 2, 3, 4 ];
+    > {{alias}}( x, 0 )
+    1
+    > {{alias}}( x, -2 )
+    3
+
+    See Also
+    --------
+

base/at/docs/types/index.d.ts

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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.
+*/
+
+// TypeScript Version: 4.1
+
+/// <reference types="@stdlib/types"/>
+
+import { Complex128, Complex64 } from '@stdlib/types/complex';
+import { Collection, AccessorArrayLike, Complex128Array, Complex64Array } from '@stdlib/types/array';
+
+/**
+* Returns an element from an array.
+*
+* @param x - input array
+* @param index - element index
+* @returns array element
+*
+* @example
+* var Complex128Array = require( '@stdlib/array/complex128' );
+* var real = require( '@stdlib/complex/real' );
+* var imag = require( '@stdlib/complex/imag' );
+*
+* var x = new Complex128Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );
+*
+* var v = at( x, 0 );
+* // returns <Complex128>
+*
+* v = at( x, 1 );
+* // returns <Complex128>
+*
+* v = at( x, -2 );
+* // returns <Complex128>
+*
+* var re = real( v );
+* // returns 5.0
+*
+* var im = imag( v );
+* // returns 6.0
+*/
+declare function at( x: Complex128Array, index: number ): Complex128 | void;
+
+/**
+* Returns an element from an array.
+*
+* @param x - input array
+* @param index - element index
+* @returns array element
+*
+* @example
+* var Complex128Array = require( '@stdlib/array/complex64' );
+* var realf = require( '@stdlib/complex/realf' );
+* var imagf = require( '@stdlib/complex/imagf' );
+*
+* var x = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );
+*
+* var v = at( x, 0 );
+* // returns <Complex64>
+*
+* v = at( x, 1 );
+* // returns <Complex64>
+*
+* v = at( x, -2 );
+* // returns <Complex64>
+*
+* var re = realf( v );
+* // returns 5.0
+*
+* var im = imagf( v );
+* // returns 6.0
+*/
+declare function at( x: Complex64Array, index: number ): Complex64 | void;
+
+/**
+* Returns an element from an array.
+*
+* @param x - input array
+* @param index - element index
+* @returns array element
+*
+* @example
+* var x = [ 1, 2, 3, 4 ];
+*
+* var v = at( x, 0 );
+* // returns 1
+*
+* v = at( x, 1 );
+* // returns 2
+*
+* v = at( x, -2 );
+* // returns 3
+*/
+declare function at<T = unknown>( x: Collection<T> | AccessorArrayLike<T>, index: number ): T | void;
+
+
+// EXPORTS //
+
+export = at;