README.md

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dlastIndexOf

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

Usage

To use in Observable,

dlastIndexOf = require( 'https://cdn.jsdelivr.net/gh/stdlib-js/blas-ext-base-dlast-index-of@umd/browser.js' )

To vendor stdlib functionality and avoid installing dependency trees for Node.js, you can use the UMD server build:

var dlastIndexOf = require( 'path/to/vendor/umd/blas-ext-base-dlast-index-of/index.js' )

To include the bundle in a webpage,

<script type="text/javascript" src="https://cdn.jsdelivr.net/gh/stdlib-js/blas-ext-base-dlast-index-of@umd/browser.js"></script>

If no recognized module system is present, access bundle contents via the global scope:

<script type="text/javascript">
(function () {
    window.dlastIndexOf;
})();
</script>

dlastIndexOf( N, searchElement, x, strideX )

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

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.
• strideX: stride length.

If the function is unable to find a search element, the function returns -1.

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:

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 views.

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.

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 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

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

<!DOCTYPE html>
<html lang="en">
<body>
<script type="text/javascript" src="https://cdn.jsdelivr.net/gh/stdlib-js/random-array-discrete-uniform@umd/browser.js"></script>
<script type="text/javascript" src="https://cdn.jsdelivr.net/gh/stdlib-js/blas-ext-base-dlast-index-of@umd/browser.js"></script>
<script type="text/javascript">
(function () {

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 );

})();
</script>
</body>
</html>

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Notice

This package is part of 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, see the main project repository.

Community

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License

See LICENSE.

Copyright

Copyright © 2016-2026. The Stdlib Authors.