blas-ext-base-dlast-index-of

Return the last index of a specified search element in a double-precision floating-point strided array.

https://github.com/stdlib-js/blas-ext-base-dlast-index-of

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Keywords

array blas double element find float float64 float64array index javascript ndarray node node-js nodejs search stdlib strided

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Return the last index of a specified search element in a double-precision floating-point strided array.

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Host: GitHub
Owner: stdlib-js
License: apache-2.0
Language: JavaScript
Default Branch: main
Homepage: https://github.com/stdlib-js/stdlib
Size: 270 KB

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array blas double element find float float64 float64array index javascript ndarray node node-js nodejs search stdlib strided

Created 6 months ago · Last pushed 6 months ago

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We believe in a future in which the web is a preferred environment for numerical computation. To help realize this future, we've built stdlib. stdlib is a standard library, with an emphasis on numerical and scientific computation, written in JavaScript (and C) for execution in browsers and in Node.js.

The library is fully decomposable, being architected in such a way that you can swap out and mix and match APIs and functionality to cater to your exact preferences and use cases.

When you use stdlib, you can be absolutely certain that you are using the most thorough, rigorous, well-written, studied, documented, tested, measured, and high-quality code out there.

To join us in bringing numerical computing to the web, get started by checking us out on GitHub, and please consider financially supporting stdlib. We greatly appreciate your continued support!

dlastIndexOf

Return the last index of a specified search element in a double-precision floating-point strided array.

## Installation ```bash npm install @stdlib/blas-ext-base-dlast-index-of ``` Alternatively, - To load the package in a website via a `script` tag without installation and bundlers, use the [ES Module][es-module] available on the [`esm`][esm-url] branch (see [README][esm-readme]). - If you are using Deno, visit the [`deno`][deno-url] branch (see [README][deno-readme] for usage intructions). - For use in Observable, or in browser/node environments, use the [Universal Module Definition (UMD)][umd] build available on the [`umd`][umd-url] branch (see [README][umd-readme]). The [branches.md][branches-url] file summarizes the available branches and displays a diagram illustrating their relationships. To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.

## Usage ```javascript var dlastIndexOf = require( '@stdlib/blas-ext-base-dlast-index-of' ); ``` #### dlastIndexOf( N, searchElement, x, strideX ) Returns the last index of a specified search element in a double-precision floating-point strided array. ```javascript var Float64Array = require( '@stdlib/array-float64' ); var x = new Float64Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, 3.0, -1.0 ] ); var idx = dlastIndexOf( x.length, 3.0, x, 1 ); // returns 6 ``` The function has the following parameters: - **N**: number of indexed elements. - **searchElement**: search element. - **x**: input [`Float64Array`][@stdlib/array/float64]. - **strideX**: stride length. If the function is unable to find a search element, the function returns `-1`. ```javascript var Float64Array = require( '@stdlib/array-float64' ); var x = new Float64Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, 3.0 ] ); var idx = dlastIndexOf( x.length, 8.0, x, 1 ); // returns -1 ``` The `N` and stride parameters determine which elements in the strided array are accessed at runtime. For example, to search every other element: ```javascript var Float64Array = require( '@stdlib/array-float64' ); var x = new Float64Array( [ -2.0, -1.0, 3.0, -5.0, 3.0, 4.0, -1.0, 0.0 ] ); var idx = dlastIndexOf( 4, 3.0, x, 2 ); // returns 2 ``` Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views. ```javascript var Float64Array = require( '@stdlib/array-float64' ); // Initial array: var x0 = new Float64Array( [ -2.0, 3.0, -6.0, -4.0, 5.0, 3.0 ] ); // Create an offset view: var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element // Find index: var idx = dlastIndexOf( 3, 3.0, x1, 2 ); // returns 2 ``` #### dlastIndexOf.ndarray( N, searchElement, x, strideX, offsetX ) Returns the last index of a specified search element in a double-precision floating-point strided array using alternative indexing semantics. ```javascript var Float64Array = require( '@stdlib/array-float64' ); var x = new Float64Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 3.0, -1.0, 0.0 ] ); var idx = dlastIndexOf.ndarray( x.length, 3.0, x, 1, 0 ); // returns 5 ``` The function has the following additional parameters: - **offsetX**: starting index. While [`typed array`][mdn-typed-array] views mandate a view offset based on the underlying buffer, the offset parameter supports indexing semantics based on a starting index. For example, to access only the last three elements of the strided array ```javascript var Float64Array = require( '@stdlib/array-float64' ); var x = new Float64Array( [ -2.0, 1.0, 0.0, -5.0, 4.0, 3.0, 3.0, -1.0 ] ); var idx = dlastIndexOf.ndarray( 3, 3.0, x, 1, x.length-3 ); // returns 1 ```

## Notes - When searching for a search element, the function checks for equality using the strict equality operator `===`. As a consequence, `NaN` values are considered distinct, and `-0` and `+0` are considered the same.

## Examples ```javascript var discreteUniform = require( '@stdlib/random-array-discrete-uniform' ); var dlastIndexOf = require( '@stdlib/blas-ext-base-dlast-index-of' ); var x = discreteUniform( 10, -100, 100, { 'dtype': 'float64' }); console.log( x ); var idx = dlastIndexOf.ndarray( x.length, 80.0, x, 1, 0 ); console.log( idx ); ```

## C APIs

### Usage ```c #include "stdlib/blas/ext/base/dlast_index_of.h" ``` #### stdlib_strided_dlast_index_of( N, searchElement, \*X, strideX ) Returns the last index of a specified search element in a double-precision floating-point strided array. ```c double x[] = { 1.0, 2.0, 3.0, 2.0 }; int idx = stdlib_strided_dlast_index_of( 4, 2.0, x, 1 ); // returns 3 ``` The function accepts the following arguments: - **N**: `[in] CBLAS_INT` number of indexed elements. - **searchElement**: `[in] double` search element. - **X**: `[in] double*` input array. - **strideX**: `[in] CBLAS_INT` stride length. ```c CBLAS_INT stdlib_strided_dlast_index_of( const CBLAS_INT N, const double searchElement, const double *X, const CBLAS_INT strideX ); ``` #### stdlib_strided_dlast_index_of_ndarray( N, searchElement, \*X, strideX, offsetX ) Returns the last index of a specified search element in a double-precision floating-point strided array using alternative indexing semantics. ```c double x[] = { 1.0, 2.0, 3.0, 2.0 }; int idx = stdlib_strided_dlast_index_of_ndarray( 4, 2.0, x, 1, 0 ); // returns 3 ``` The function accepts the following arguments: - **N**: `[in] CBLAS_INT` number of indexed elements. - **searchElement**: `[in] double` search element. - **X**: `[in] double*` input array. - **strideX**: `[in] CBLAS_INT` stride length. - **offsetX**: `[in] CBLAS_INT` starting index. ```c CBLAS_INT stdlib_strided_dlast_index_of_ndarray( const CBLAS_INT N, const double searchElement, const double *X, const CBLAS_INT strideX, const CBLAS_INT offsetX ); ```

### Examples ```c #include "stdlib/blas/ext/base/dlast_index_of.h" #include int main( void ) { // Create a strided array: const double x[] = { 1.0, -2.0, 3.0, -4.0, 5.0, 3.0, 7.0, -8.0 }; // Specify the number of indexed elements: const int N = 8; // Specify a stride: const int strideX = 1; // Perform a search: int idx = stdlib_strided_dlast_index_of( N, 3.0, x, strideX ); // Print the result: printf( "index value: %d\n", idx ); } ```

* * * ## Notice This package is part of [stdlib][stdlib], a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more. For more information on the project, filing bug reports and feature requests, and guidance on how to develop [stdlib][stdlib], see the main project [repository][stdlib]. #### Community [![Chat][chat-image]][chat-url] --- ## License See [LICENSE][stdlib-license]. ## Copyright Copyright © 2016-2025. The Stdlib [Authors][stdlib-authors].

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Standard library for JavaScript.

Citation (CITATION.cff)

cff-version: 1.2.0
title: stdlib
message: >-
  If you use this software, please cite it using the
  metadata from this file.

type: software

authors:
  - name: The Stdlib Authors
    url: https://github.com/stdlib-js/stdlib/graphs/contributors

repository-code: https://github.com/stdlib-js/stdlib
url: https://stdlib.io

abstract: |
  Standard library for JavaScript and Node.js.

keywords:
  - JavaScript
  - Node.js
  - TypeScript
  - standard library
  - scientific computing
  - numerical computing
  - statistical computing

license: Apache-2.0 AND BSL-1.0

date-released: 2016

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@stdlib/array-float64 ^0.2.2 development
@stdlib/array-one-to ^0.2.2 development
@stdlib/assert-is-browser ^0.2.2 development
@stdlib/assert-is-integer ^0.2.2 development
@stdlib/bench-harness ^0.2.2 development
@stdlib/math-base-special-pow ^0.3.0 development
@stdlib/random-array-discrete-uniform ^0.2.1 development
istanbul ^0.4.1 development
proxyquire ^2.0.0 development
tap-min git+https://github.com/Planeshifter/tap-min.git development
tape git+https://github.com/kgryte/tape.git#fix/globby development
@stdlib/assert-is-error ^0.2.2
@stdlib/blas-base-shared ^0.1.0
@stdlib/blas-ext-base-dindex-of github:stdlib-js/blas-ext-base-dindex-of#main
@stdlib/napi-argv ^0.2.2
@stdlib/napi-argv-double ^0.2.1
@stdlib/napi-argv-int64 ^0.2.2
@stdlib/napi-argv-strided-float64array ^0.2.2
@stdlib/napi-create-int32 ^0.0.2
@stdlib/napi-export ^0.2.2
@stdlib/strided-base-stride2offset ^0.1.0
@stdlib/utils-define-nonenumerable-read-only-property ^0.2.2
@stdlib/utils-library-manifest ^0.2.2
@stdlib/utils-try-require ^0.2.2

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